Do you also have a lot of cucumber beetles in the flowers? I have some looking the same and I suspect cucumber beetles but I am also very new so I don't know.

Hi George, I have seen a couple of beetles on the property last year...but none this year. I am leaning towards overwatering (which often looks like underwatering). My moisture meter only goes about 8 inches deep...but it is always in the "moist" reading. Waterlogged roots can not breathe...and hence they pull up no nutrients or water. My only other concern is cucumber mosaic virus...which my plants had last season. The jury is still out....

What about temps? Where are you at?

mild temps in the 80's. Perhaps I over-watered in my clay soil? Or maybe cucumber mosaic virus...I had that in my cukes last year.

Looks like yellow vine decline disease to me.