Give us some idea of where you are geographically and what kind of care you've been giving it and it's current environment. Watering, fert, temperature, humidity, etc.

What size container is it in and what type of soil is it planted in? You say it's been in that container for a long time, how long?

So the container is 18" interior diameter at the top, 17" deep, and then about 12" diameter at the bottom. It's a plastic container. I have it planted in Premium Cactus mix which I was told is best for citrus trees, and I tossed in some citrus fertilizer about 3 months ago when we repotted it from a smaller pot. So It's been in this new pot for probably about 3 months now, as it has grown bigger.

Leaves have a lifespan, when they get old they yellow than fall off, can't say for certain that's what happening. Give us a pic of the whole tree and container. You should also be fertilizing a container plant every two weeks or so preferably with a water soluble fertilizer as close to 5-1-3 as you can find. The cactus mix isn't the best, but it's far from the worst.

Good to know about the fertilizer! I wasn't necessarily doing that too much and so I think maybe it's just really craving nutrients? Full photo below:

Is your soil mounded up out of the pot around the rootball? I would almost wonder if the water isn't running off the surface of the soil and part of your rootball is dry. Do you check moisture?

My tree was mounded 4 inches above the pot. I used a sprayer to water mine so the water didn't run off. 3 gallons over a 2 hour period sitting in a tub to catch and hold water to be reabsorbed.

Steve

That's what I'm asking, in other words, how is the tree being watered? If just over the ground mounded in that way, part of the soil may not be getting water.

I've just been using a hose with a soaker attachment, spraying as much in as it can handle without the water spilling off the sides, and then waiting for that to soak in before filling it up again. So you might be able to see a bit of a lip I've created with the soil so that it almost creates a little pool for the water to not run off the sides. If I had to guess how much I'm watering this way, typically it'll twice a week, maybe 2 gallons each time. About a month ago before this all started though I was worried I needed to water it a lot more since it started fruiting, so I was more so doing 2 gallons probably 4 times a week. Is it possible I flooded the tree and this could be root rot?

What fertilizers and how much?