Summer squash leaves
Isabella County Michigan
Hello. Did you notice anything on the leaves before they turned brown? If so, can you send a photo of a leaf before it turns brown? Thank you.
No, they went right from yellow to brown.
Without anything else to go on this looks like this may be bacterial wilt suggested by the interveinal chlorosis /necrosis and sudden onset. Check out the following links:
Nutrient imbalances can also show similar symptoms: