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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.
Leaf curl on citrus usually means over watering. The fruit being lighter from nutrition problems.
How big is this tree, and what's your water and fertilizer schedule?
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.
Leaves curling up plus sunscald on the fruit.
You either moved it to a sunnier spot than it was used to or the temperature lately has been hotter than it is acclimatized to.
Like much of the world, we have had some days that are hotter than typical for us. I'm in the PNW.
Daily watering for an hour is defintiely too much for potted citrus - try getting a smart water timer that can do 2-3 times weekly instead, it'll save your trees and still keep the automation you need!
The problem is that the schedule has been working well for my veggies and herbs. It's not a full hour on the pot because the sprinkler rotates, but I am getting the impression that it's too much for citrus anyway.
Small frutis might mean it is too cold. It could also lack nutrition.
You should think about different conditions (how wet is the soil, have i provided enough nutrients, what was the temperature) and cross-off different causes of this.
The fruit size looks right. Sudachi are very small. I do think I might be overwatering and it might be getting too much sun. I think I will try moving it to an area on the periphery of the sprinkler where it gets a little more shade. Also do a soil test once I can grab a test kit.