new..here are some guide lines, water Indoor containers every 5 to 7 days (1/4 to 1/2 gallon).A moisture meter would be good.With your yellow foliage there are 2 possibilities.Lack of fertilizer or over watering to the point that the root tips are rotting and not taking in the nutrients needed.Be sure to fertilize properly. If it was mine..I'd take the citrus and water throughly like put it into the shower,and water until it's running out of the bottom of the container.Let it sit there for awhile to drain. Take a 1/2 gallon of water and mix into it (1) Tablespoon of MIR-ACID, miricle grow makes it.Mix it up good and then pour this into your soil around the dripline inside the container.This way you've flushed the soil of most of the salt build up and you've fertilized your citrus.I use Mir-Acid on my citrus trees every month.Plus I also feed citrus food 4 times a year.Then put it back into the light and leave it alone for quite awhile.If it doesn't perk up then it's probably rotting root tips,if this is the case dig up your tree,trim the roots and re-pot into new sterile soil with some added bark mixed in for drainage. GOOG LUCK...this tree has taken care of you ,now you have to take care of her.***Suzanne

thanks, Suzanne. So it doesn't look like a mineral thing? because feeding it (and using Super thrive) seem to have made it worse so far.

Cheryl

I also have a meyer lemon but mine's in the ground, is more than 10 years old, and I'm in SoCal. But I noticed that you're a new gardener so I just want to mention...
When the weather cools down, fall/winter, citrus usually slows down it's growth, often stops. Unless the temps are comfortably warm and lighting is bright, it's usually good to just "maintain things along"(everything done in moderation). Even my well established meyer gets yellowing leaves, like your pics show, during winter, maybe from poor nutrient uptake due to cold or overwet soil, but recovers come spring.

Meyer lemons are pretty hardy, your leaves don't seem too bad. Spring will come around soon enough to get the new leaves growing.

Cheryl, Superthrive is very helpful, but if a tree has been over and under-watered a number of time, NOTHING will bring a dead tree back.
Since you've been feeding, I'd withhold food until spring. I think you're trying to force growth on a tree that is trying to rest.
One thing is improve the environment. If the temp is 55 degrees or ever in this room, I'd remove the lights. I can see this done if a tree is outdoors or in a totally unheated room, but not in your heated house.
Next I'd make sure the house has adequate humidity. 50% or higher. NOt only is humiditity good for plants but people, too. Thirds, air circulation is important. A ceiling fan, even in an adjactent room helps circulate heat and humidity.
Checking for insects is important, especially this time of year. Your leaves are yellowing for a reason. It could be the reasons Suzanne mentioned, and/or it can be bugs or iron deficiency. I wonder about the definciency since you mention the veins protruding color, more pronounced.
Shake the tree to remove yellowed leaves, and lift felled leaves from the soil..leaving them will only attract insects, including fungus gnats.
It's important familiarizing yourself with proper waterings. water only when top 3" of soil is dry. You can either stick your finger in the soil..if it comes out moist wait a few more days and check..if dry, then water. Another way it to life pot..if it feels light then most likely it needs watering..If heavy do not water, and do the finger test.Good luck, Toni

thank you so much for all of your help and suggestions! I will be trying a bunch, and will post how it goes. it really means a lot to me to get all this help!

take care,

cheryl

Cheryl, no problem..that's what 'we're' here for..Keep us informed on the progress of you plant..
When you'll said you'll be using a bunch of it, what did you mean? If you were talking about Superthrive/fertilizer, please don't overdo it. Use sparingly, especially during winter months. Good luck, Toni