It kind of looks like some of the leaves may have been exposed to herbicide drift. Any chance of someone spraying herbicide in your area. If the damage showed up virtually overnight that may explain it. It also could be damage from various leaf sucking bugs of which Aphids are one. Cucumber beetles and squash bugs could be another possibility but you said you have only seen aphids on them.

No chance of an herbicide I live on a balcony with no other plants near me. I only seen very few aphids as far as pests and the only kind of "insecticide" I have used is soapy water.

Your picture looks a little bit like on-line graphics of anthracnose. Do the spots turn brown?

I do not think it is anthracnose that seems to mainly affect trees. The spots turn as brown as they get in the picture. I am thinking it is Angular leaf spot.