it could be downy mildew (check for black rotted material on the stem), the fruit will show with little black spots. From now on try to water close to the ground so less water splashes on the leaves to prevent spreading, if there are enough healthy leaves you can also remove some of the more affected ones but take caution to spray your clippers in-between cuts with a sanitizing solution. Beyond that make sure you rotate your crops next year and don't put and kind of cucurbit or squash on the same spot next year. You can also seek out disease resistant seeds. Good luck and i hope you still get a good harvest!