It could be too much light for the heat of the roots, if you are lucky,they like about 70F to 90F with strong light but it does sound more like it got too wet

You need to make sure the compost is drying out, do not water it untill it drys out, if it has had no holes in the pot than that will be the problem, it could be the potting mix
When you replanted it did you use dry compost?, if so it will probably be ok, but it may still loose leaves, as damage has been done, let it dry out, keep its roots warm (70+F)
With root rot, if it is root rot (probable) the roots will stop working till they recover, so feed it every now and then , once a week or so by misting dilute citrus fertiliser onto the leaves and stems, not the compost

Dont disturb its roots anymore if they are dry enough,when it recovers it would be a good idea to use a citrus compost with added 30 to 50% perlite or chc, and not to have the rocks in the bottom of the pot, they can cause water to collect under the roots it prevents the pot draining as well and it can rot the roots, you are better just with larger drainage holes in the pot and a good potting mix.
If the roots are still very wet, repot it in a fairly small pot with lots of drainage holes , with a free draining compost
If you put a photo up someone will be able to see for nutrient defficencys and pests etc

Starloc sounds right...root and heat problems are the likely cause. With the light it is currently under, it needs AT LEAST 15c temps, probably warmer if you can manage, in the root zone. At 10c the roots aren;t working, so can;t transport water to the leaves for cooling and health and therefore the leaves shed to avoid burning.

Check the roots if poss, make sure they aren't rotting. Let the potting mix (which should contain no more than 1/3 comport, rest should be perlite/chc/bark chips etc) dry out somewhat between waterings - having constantly moist roots will harm the tree.

Pluck the lemons off. By nearly ripe, do you mean nearly fully yellow? Lemons need picking when still half green, not when fully yellow. The tree is using valuable energy keeping hold of the fruit - clip them off and let it recover.

As starloc said, do not give it any fertilizer in the compost. It'll do more harm than good until it is healthy. Place the tree on a humidity tray if it is indoors but make sure the pot isn't sitting in water. And yes, a pic would be good :)

Citrus are extremely resilient, and spring back into life from the lowest sign of life sometimes, so all is not lost. It may not do much for a number of months, but with some good treatment and proper care, come spring you might end up with an entirely healthy and fresh lemon tree :)

Oh, and brown edged leaves?....could be a sign of salt buildup in the soil. How often do you fertilize, and with what?

You wrote: "have even replanted the tree in a pot with holes, and rocks at the bottom for drainage!"

The drainage holes are good. The rocks at the bottom aren't.

Contrary to popular opinion, coarse stuff in the bottom of pots makes things worse, not better.

At a glance, that coarse stuff sounds like it should work. After all, it has large holes where the water should be able to go.

But not so.

The problem is in soil physics, namely the movement of water from one texture (the potting mix) into a different texture (the rocks).

The water won't move into that coarse layer until the layer above it (the potting mix) is saturated.

The water will not flow downward into the coarse layer unless the overlying "soil" is above field capacity, but this is far less wet than saturation. (Flow here meaning in pores between soil grains or as films upon them.) The coarse grains at bottom simply help (by increasing permeability and reducing this layer's field capacity) to shunt the water to the drainholes and avoid greater sogginess (wettness closer to true saturation) in a thick bottom zone. Instead, saturation (when it occurs briefly after heavy watering) doesn't exceed a very thin zone at the base of the coarse material. To me, a thin zone of coarse material, while not essential, also helps gas exchange with the base of the soil. This is more important with heavy soils used for such plants as palms.

When i buy a pot i cut holes like this all around the edges, these holes are 2.5 inch by 1/2 inch wide they go underneath by about an inch

Here is a link that might be useful:

About the coarse stuff in pots which doesn't help with drainage, read this research-based info.

"Physical Characteristics of Growing Mixes" at

http://ohioline.osu.edu/hyg-fact/1000/1251.html

If you don't want to read all of it, please scroll to the header "Watering Containers."

As I said previously, coarse stuff in the bottom doesn't help drainage. Further, it will make things worse.

Here is a link that might be useful: drainage in pots

Very odd. He indeed says that and shows it in a figure, but offers not the slightest explanation. That is simply not how drainage of a porous medium works. Only clayey soils (and maybe very fine grained dense mucks) can hold water against gravity at anything approaching saturation (~95% saturation at field capacity). Such soils are not used in pots, quite the opposite. It is easy to see that he is wrong in the general sense. Imagine that the potting soil is pure sand, or coarse sand, or perlite. These can never hold water against gravity at anything near saturation. I wonder where he got this idea? He is a horticulturist, not a soils physicist I note. I think it is myth, but it does have me intrigued enough to look into it later.

It was said "but offers not the slightest explanation"

He may be a horticulturist but he was reporting research-based information.

Beyond that, I thought that the illustration with pots would help folks understand what occurs.

Water has the same problems moving between 2 different textures whether in the ground or in containers filled with potting soil.

The junction between the two different textures is termed an interface. I suggest to my students that they consider it as a "barrier" because it seems they can understand the concept more easily that way.

As I previously said, slightly modified, the problem is in soil physics, namely the movement of water from one texture (the soil or potting mix) into a different texture (the rocks or other coarse stuff).

You'll find lots of information if you use google with the search phrase "stratified soils" or "water stratified soil" -- but without the quotes.

The following is a brief excerpt from Virginia Tech at
http://clic.cses.vt.edu/icomanth/soilmodi.html

"Water does not move uniformly downward in stratified soils. Fine layers underneath coarse layers will slow down the rate of water percolation through the smaller pore spaces. This builds up a temporary saturated zone above the fine layer, and the results in poor aeration of plant roots in that zone. If the fine layer is above the coarse layer, almost the same thing happens, but for a different reason. In this case the smaller pores in the fine layer hold onto water more tightly and will not release it across into the coarse layer until the fine layer becomes completely saturated. Again a poorly aerated zone is created, and this on may last longer than the first one. Because of these discontinuities in water-air relations in stratified soils, roots do not grow uniformly in them. Roots often will not penetrate downward through a layer of contrasting texture, even though it may be less than an inch thick."

Here is a link that might be useful: water movement in stratified soils - research-based info

"In this case the smaller pores in the fine layer hold onto water more tightly and will not release it across into the coarse layer until the fine layer becomes completely saturated."

I had wondered if it might relate to difficulties yielding to the sparser surface films of the coarser materials below. But still, this says it can saturate if "fine," not "finer." Potting soils aren't anywhere near fine in the soil sense, not silt size far less clay size. This simply could never happen with gravel over boulders, for instance, so it can not be a general rule (finer over coarser). You wonder how fine everything has to be for it to be operative and if common potting soils are in that range. This also would imply that an experimental sand column (say above a screen or a sintered [same grain size] sand plug) could support a saturated zone over open air, and this simply is not so. At best by this process the descending saturated zone would slow down a bit at the bottom. UNLESS all they are talking about is the thickness the material could support a capillary zone (which it won't give up) but that would be a pretty trivial case.

Thanks for the reference. I look forward to reading and seeing what all this is about.

The info I used is among the basic principles you'll learn in a college-level soils class. If you have a nearby community college, check to determine if has a horticulture program and offers such info.

If you go back to the 1st link I added, then again look at the pot illustrations, it shows which region of the potting mix is saturated during which conditions.

Those illustrations are accurate when growing in non-porous pots. The blue area is where the saturated media exists.

Using permeable clay pots would change things because water is also lost through the sides of the container.

Even without coarse stuff in the bottom of a non-porous pot, a thin layer of saturated media is at the bottom after one irrigates the pot, then allows it to drain until the dripping stops. The reason is that you still have an interface -- from the texture of the potting media to that of air.

Boy, I'm having problems finding anything other than extremely technical stuff.

But finally found this 20-page piece from No. Carolina State (NCSU) which may be lots more than any of you folks care to wade through. (NCSU is a leader in container production research.)

http://www.ces.ncsu.edu/depts/hort/nursery/cultural/cultural_docs/substrates/container-soiless-media.pdf

Here are some specifics for this thread.
1. page 2, under the headings Container Effect, also Height of Column (the sponge demo is in Figs 5-8)
2. The figures referred to begin on page 16
3. Illustration of coarse stuff in the bottom (Fig 9) is on page 17

So, this piece also explains another challenge, so to speak, for drainage in containers.

As has been said, particle size is important (in general, larger is better). Another key factor is height of the container (deeper is better).

Here is a link that might be useful: NCSU re drainage & more in containers

if anyone would like to see some pictures, i would be more than happy, grateful actually if you would like to look at them!!! one thing i forgot to mention, i am using a fertilizer, meant for citrus trees. it is a series af tablets buried into the soil that release nutrients when watered. they last about a year, and feed the plant slowly over that time frame (8-4-8). www.treehelp.com, i added the link
thanks and happy holidays

Here is a link that might be useful: treehelp citrus fertilizer

Yes, it could be helpful if you post images.

here is a thread in the container forum about Container Soils - Water Movement & Retention V and why not to use a drainage layer.
There is a lot of information on that thread, and it's fairly easy to understand.

I have my Meyer Lemon in the gritty mix (1 part each of bark / turface / small gravel) and it is growing well.

I look at it this way in simpler terms of course.....
I am brain dead and bored, so here it goes..lol
I if don't make sense, pardon me.

If I can't or do not know how to grow anything in a pot with a Perched Water Table, which I mostly do not, then I won't use a soil that encourages it. Using bottom stones, or even water proof packing peanuts which don't weigh the pot down never helped me. By the way, if your determined to use bottom material, this is the way to go. No more heavy pots.:-)
I have killed a many plants in the past this way. The bottom roots being wet ,stuck in that PWT above the stones, never drying out while the top half of the roots keep getting watered because I keep watering the top of soil that is bone dry. My roots can be thirsting for water even 4 inches down into my pots from the top, while the bottom half of the roots are in that PWT portion staying wet, never drying out. And rocks on the bottom of any pot does not get rid of that PWT. It just makes it higher. The Perched Water Table depending on the soil you use will be there, and maybe not if you use a wick or a fast draining soil.
Of course this is not a concern to me in any pot smaller than 6 inches... They dry out fast, especially if they are in clay. I typically use something other than the gritty soil for these. But when I move up to a bigger pot, I am not willing to take the risk of root rot. Some people here can grown plants in any size pot with a PWT and have sucess. Some in 30 gallon barrels! I am not one of those..:-(

This is why I use A'ls gritty mix minus the fines that could settle down at the bottom of pot and stay wet while the top of the soil gets dry.

Bonsai have very shallow roots, therefore grown in shallow pots, and this is how a many of my friends including myself have killed our Bonsai. You can have a PWT in soil as deep as one inch. We can't afford to have a PWT at all in such shallow pots! On this we take NO chances. I can not afford to have a PWT also in big sized pots for regular plants.
Since they and I changed to Al's gritty mix, we have been sucessful, with no Perched Water Table and bottom root rot, even in rainy everday weather if pots are left out all summer. We just have to water more often when because the soil dries out quicker. :-)

Jean, I have done the same thing to most of my pots, especially the ones my Clivias are in. They are thriving!! I even drill bigger holes at the bottom of my plastic ones and hammer out a huge circle hole on the bottom of my clay ones, then use screen to stop the soil from falling through. I can only imagine the roots breathing all that air from the bottom!lol,and the water exchange because of this.:-)

I love that Container Soils thread, at least what I can understand of it! One thing I did learn, I never knew what a PWT was until I read that thread. That was the culprit to the death of all my plants! Thanks for that thread Al!
Thanks for all the great info everyone!
Take care all!
Mike