Of course I agree with Jon on all 3 points. Where are you located? Some zones have hotter sun than others.
I took a walk through our plantings today and noticed several figs with yellow dropping leaves. I took my soil sleuth (google that), and checked the soil. Dead dry! And they are all on drippers. Well, we turned the thing on, and guess what? HUGE leak making all the figs and grapevines get less water than they should. It's now fixed. We don't notice the leaks usually because it's set to water at 5 AM. We are asleep at that time.
I suggest you buy some kind of soil water meter. The sleuth is cheap, and you could even make it yourself. BUT, it goes into the soil, you turn it, pull it up, and if the soil stays in the notches, it's damp enough, but if it poofs out... too dry.
Suzi