Year after year my dwarf valencia will set some fruit, it will get to marble size, shrivel and fall off.

This year I realized I wasn't feeding enough, so during fall and winter feedings did better. It responded with good growth.

I have several fruit set, almost to walnut size. I don't want to lose them. I have never had fruit from this tree. It is at least 7 years old.

I put a sheer curtain over it the other day, as it is showing leaf sunburn already. Will this be OK for all summer?

I am in Phoenix and has been hot for quite some time now. I water deeply and slowly at least once a week.