The symptom is cholorosis, a lack of chlorophyll due to micronutrient deficiency/lockout.
Mainly the tree is lacking Iron and Manganese, two elements abundant in many of the mafic soils in San Diego where housing developments are built.
If you planted on a soil abundant in these elements, the lockout is most likely due to municipal water sources which have a high pH, and after time and lots of irrigation, the soil attains a high pH. High pH makes the elements insoluble, and therefore unavailable to roots.
Too much fertilizer, especially Phosphorous can also cause lockout, but is less common.
You can have your soil tested, but I use foliar feeds high in the micronutrients Fe and Mn. If you use a simple pH test on the root zone and it comes up greater than 8, soil sulfur can treat the issue long term.
If it is a cherimoya specific issue, and citrus in the area look fine, it could be due to moisture swings in the soil.