Hi,

More info would help.
What kind of cherimoya?
How old is it?
Is it planted in the ground or in a pot?
Watering schedule?
Where in socal are you?
Is it in a north, or south facing area? or west?

that looks like over watering that happen to me with my Atemoya.

JF

I think that might be over watering as well, but it might also be from the weather (I'm in socal too) since it's been all screwed up with chilly nights and all.

Could be the heat we've been having

Yup, looks like extreme heat damage. I say this because my cherimoyas were growing nicely until the recent heat wave which caused a few leaves to turn yellow and then fall off when I watered.

Simon

To offer an opposing example, my cherimoya is in full sun, high 90s to low 100s the last few weeks, I only saw 3 yellow leaves like that.

That reminds me, I need to get a longer support rod for mine just in case the winds get high enough.