Squash disease? Solution?
Looking at the three photos that appeared with your question, I am suspicious that the problem is angular leaf spot, which would fit with wet weather that we have had recently in the Willamette Valley. The plants may recover during the hotter, drier weather if you avoid wetting the leaves. Avoid over-fertilization and do not plant any cucurbits in the affected area during the next two years as the bacterium that causes this disease can remain in infected plant debris in the soil. This pathogenic bacterium is also seedborne. See https://pnwhandbooks.org/plantdisease/host-disease/cucumber-cucumis-sativus-angular-leaf-spot for more information.
Thank you! The drier weather seems to already be slowing the spread considerably.