The fruits have started to pale and the leaves to curl. I'm pretty new to citrus.
Edit: Thanks to everyone! I'm going to try to make a couple of changes based on your suggestions.
Overwatering is likely. I have it in an area where a rotating sprinkler runs once a day for an hour (I'm disabled and I rely on automation a lot). I'd like to set up a drip system, but I keep my citrus trees in pots.
I've only had this one since spring and I haven't fertilized it yet. I do have citrus fertilizer that I have used a couple of times a year on my yuzu, which is looking healthy. I keep the trees far enough apart that they shouldn't be able to infect each other if there's a disease. I can test the soil for nutrients.
It's a young tree, 2 1/2 to 3 ft tall.