The photo of the squash foliage shows the natural vein pattern of the leaf. Looks like there may be some powdery mildew on the tip of the foliage. Infections often start when plants are mature and are rarely a problem for gardeners.
Middle photo and right photo - looks like powdery mildew on the stems and you may be dealing with squash vine borer, an insect pest. You will have to look for this. See our website for more information.