Dogwood leave discoloration
I'll need a bit more information to be sure of what might be going on. Maybe if you email me directly we can carry on a discussion best that way. This year it has not been unusual to see stress on some dogwoods, especially Cornus kousa, the Kousa or Chinese Dogwood. Leaf curl and discoloration, particularly on uppermost, sun-exposed leaves is common. And you are correct, it has been caused by environmental conditions, not disease or pests. Are your dogwoods C. kousa, and if so the same cultivar? Are they growing in sun or part shade, and are they irrigated? The pattern on the leaves is that of interveinal chlorosis, meaning the leaf veins are green and intervening tissue is chlorotic. This is often characteristic of iron deficiency on some plants. There appears to be evidence of sunburn on some of the leaves. Are some arts of the tree displaying more of the symptoms than others? Anyway, contact me directly and we'll figure this out!