Where are you located and how is your feeding schedule? It's not unusual for trees to struggle indoors during winter but come back. Good feeding and summer sun works miracles for us.

I'm interested in your air pots and how often you have to water.

Experienced something very similar last year with both a potted Meyer Lemon and a Bearss Lime in fabric pots. My ultimate conclusion was that the pots contributed to very unhappy roots, but that looks generally to me like root distress. If the plant isn't in a fast-draining, well-aerated 'soil' that you can saturate without drowning the roots, it needs to be re-potted. Repotting would also give you an excuse to give a good look at the roots. If you see weak / rotten roots, it's a clear sign something was wrong and you'll need to remove all the dead and dying roots. Some folks on here swear by a quick dip in a peroxide or bleach solution but I've never been so bold. I do treat plants that are showing signs of root or foot rot with a quarterly dosage of Agri-Fos fungicide, which has worked for me to stave off death by Phytophthora infection, but the science is hazy on weather Agri-Fos works as well in containers as it does for plants in the ground so I would say treat only if you're comfortable.

There's no reason to have boron toxicity in a potted plant unless you concocted some sort of "special" mix, one of the most common ways home gardeners create problems for their plants.

Need to know what the potting mix is.

Commercial? If so, the brand/label.

Homemade? If so, what's in it?

Last time re-potted?

I too am interested in the air pots, pricey little guys.

The plants are in Pro-mix HP mix with some added coarse perlite. As for feeding, since they were grown (from seed) they have been fed with slow release fertilizer, specifically - Lutz citrus tablets. I am absolutely clueless when it comes to all the science of gardening, but just a glance at the nutrient list says each tab contains .05% boron which is a higher level than i notice is in FP (.01%) or osmocote (.015%). They have been on these tabs for 2.5 years with none of these yellowing issues, however at the beginning of spring this year i added on or two more tabs to ea pot (the instructions call for 5 tabs for every inch of girth) and a week or two later fed each tree with a regular dose of Foliage Pro. Right afterwards they showed the yellow tips, which is why i stopped using the FP and haven't used it since. After flushing heavily, the yellowing went away or at least slowed down but only for a bit. Then it started again and hasnt really stopped, just getting progressively but slowly worse.

Jury is still out on the air-root pots in my opinion. My trees have for the most part flourished in them, until this episode...

I am assuming that if the problems happened after you increased the fertilizer that they are simply over fed and " burned" by the fertilizer. I have used FP with great results and only heard not so great things about fertilizer tabs or spikes. The tabs seem like they would be better for in ground citrus over pots since that is what they were designed for. I would flush your pot really well with 4x the pot size of water then resume a normal fertilizer schedule with just the FP, or if you insist on continuing with the tabs go back to the lower amount that didn't cause problems.

Fertilizer tablets are not a good method of giving your tree nutrition. A citrus leaf has a life span of approximately 18 months, then the tree withdraws the nitrogen from the old leaves and disperses it to areas of the tree in need. That is why old leaves turn yellow. If your tree has been growing for several years the lower yellow leaves are probably just old leaves. Sammers is correct in that the problem is certainly not boron.

In 2008 I posted a question on this forum asking what fertilizer might be best for container citrus here. I didn't get alot of answers but someone mentioned the lutz citrus tabs which are indeed made for use in containers. It could be that I over used them. I love the fact that i dont need to worry about using liquid fertilizer - besides for the expense it also takes so much more time.

The reason i thought boron as opposed to salt/over fertilizer is because the yellowing isnt spread out over all the leaves - and from what i read it seems boron tip yellowing starts specifically with older growth. Also since I saw the yellowing months ago i have made sure to flush the pots regularly at every watering. It seems that while that would help with salt toxicity, with boron thats not the case.

Maybe it is just some over fertilizing, although im not sure its just old leaves. Either way I guess I just have to give them more time to see of it straightens itself out.

It would be a very big problem for me to replace the soil on these trees - do you think it is imperative or can i just continue flushing and eventually they'll disappear?

How often are you watering? Are these plants indoors or outdoors. Yellowing and pale leaves are the first indication of overwatering. I use Citrus Tone monthly for fertilizing. Citrus can be very hard to read when it comes to watering. I have two Meyers in airpots, as well.

Rita, this is a 4 years old. But good intentions)