Fruit drop cause?

What causes fruit drop? I know some is normal and I always have some but this year has been almost total drop on my pawpaws, persimmon, hardy kiwi and citrus. I did a lot of hand pollinating pawpaw and looked to have good fruit set but almost all ended up dropping. 2 year old Issai kiwi bloomed for the first time but dropped all fruit. Not so worried about that because it is young and have read that is not so unusual. My persimmon is almost done blooming and has dropped all fruit that has done flowering.
I have not had this problem in past years.

We’re in a heat wave with no rain, so I’d water them daily. I have one
peach tree that’s been dropping fruit, so I started watering it and it’s
stopped dropping, and looks a lot happier…

Some of my Satsuma plums turn yellow and drop. No bite marks or anything else noticeable. Some fruits just stop growing, turn color and drop. Is this just normal June drop?