Any number of things could be causing it. Holes in leaves are pretty common in a garden and unless they get really extensive they don't do any harm to the plants.

Would need to see a close up picture of the leaf damage to even begin to guess. Flea beetles is just one possibility so you might check into them. But the damage they do doesn't hurt the plant.

Squash bugs, stink bugs, small slugs, even wind and/or mulch are some other possibilities.

Dave