Are your leaves bleached looking or does it have a flocked like fuzzy appearance? Are they small spots like an insect had been sucking? It's hard to say without actually seeing the plant

If it's fuzzy or flocked looking it is mildew. Small dots it's insects.

If they are bleached looking it is not disease or an insect. Could they be from the sun on droplets of water burning them. That was my first guess after I read your post