Yellow leaf margins on curcubits
I have a number of squash and cucumber plants that display yellow leaf margins. The yellow color becomes broader until the leaf dies. New leaves are also affected.
The plants are in full sun (highs in the low 90s) and soil moisture is adequate but not excessive. Some sick plants are twenty feet from other sick plants and there are watermelon plants between that aren't affected.
I checked out photos of plant diseases and none seem to match.