Why would my pumpkin, cukes, and melon plants get yellow spots on leaf
Related Discussions
Suggested Project Book
I recently read that water spots on leaves during the heat of the day can act as a magnifying glass and burn your plants.
It may be the beginnings of powdery mildew. Contact your local extension office to be sure.
Hope that helps
https://smfarm.cfans.umn.edu/pests-and-diseases/identification-information/cucurbits