Thanks Kelley! I'm still on the fence about how well my tree is doing but so far it doesn't look like there's any large infestations or obvious diseases. The only explanations would have to be root rot, lots of fungus gnat larvae, or not enough food for the tree. And I'm hoping it's not the root rot! With your mix, it might be due to the fact that each of those materials hold water very well. From all the research I've looked at online, vermiculite and perlite are usually recommended to be chosen for just one or the other in most soil mixes. Or a mix of both to equal 1 part. The only time I've seen a mix include both as separate parts was IVOrganics on YouTube but I didn't stay updated on how the tree fared. If your vermiculite was a larger, coarser type then it might be ok? I've read vermiculite tends to hold water very well due to absorption while perlite just gets wet on its surface. Is your lime also on that same mix? It probably is just the mix's drainage...I think an expert should give you a more informed opinion on your eureka. I've had my first lemon for only a month now. My advice would probably be to not listen to my advice lol

Salt buildup. After flushing the soil the new leaves will be fine but the afected one will still die. Your tree is begging you to remove the pot with soil from the bigger fake one. Carbon dioxide is heavier than air and it will acumulate inside the big pot, suffocating the roots. Roots needs oxigen!

Ali, Steve made a great point! At least 16 hours of light by now. What kind of light is that and how strong is it? Does it get any sunlight at all in a south facing window? You could use any good soilless mix you find there, but youwould have to gauge how fast it dries and whether or not it's good for the environment you have it in. Options You could use a clay pot with a good soilless mix. Miracle grow will work if you add more perlite to it, or even bark mulch, pine that is. You could use straight 'pine bark' or 'hemlock mulch with added lime. That would be very porous. You could use the mulch with added perlite even more porous. You could use mulch mixes with peat and perlite. As you can see, there are options, just become creative with a mix that does not hold perched water and that can rot or suffocate your roots. In your situation you most likely need a mix that is very porous and that dries out evenly and quickly like within a couple of days which I likje ro wthin at least a week. ) I wish everyone that grew citrus in containers could understand the concept or how water behaves in planted containers and how to make mixes work best for their trees and grower. There is plenty to learn at the container forum if you ever wanted to know more) While you stay safe, here is something you might enjoy reading) https://www.gardenweb.com/discussions/5894651/container-soils-water-movement-and-retention-4-11-20#n=14

@bonsai_citrus_and_indoor_gardening See photos. Some other info: I accidentally over fed the tree mid-summer with citra-tone but it's my understanding that since citra-tone is all organic, it's harmless to "overfeed" and we didn't get any fruit or flowers until I did that. The grow bulbs are pretty weak so we have them kind of close. I had some leaves with eggs underneath in mid summer but i plucked them and some munchers (worms in the curl of leaves, idk what they're called) in the leaves but again, got rid of them. Haven't seen any of either pest since. before i took the tree in, it rained a lot so the soil was pretty soaked so I haven't watered it since and it still looks like there's moisture in it soil. I'm also pretty sure the fungus gnats are a consequence of bringing it in while it was so wet. Thank you so much for your help! Also included a picture of the one lemon that came from the single february bloom, it's huge and super healthy and we didn't harvest it until this week so I don't think the tree is totally failing. 1. Single lemon that started in March after a single Feb bloom 2. Current moisture situation. Meter is about 3-4 inches deep 3. current lemons and blooms. Lemons are about an inch long 4. Grow bulb positions, there is a large window adjacent to this corner but doesn't get a whole lot of direct light through it due to the neighbor's house being about 10 ft across from it.