Or, did you have a hail storm recently? Those holes look torn and not eaten to me, too.
Meant to add, have you fertilized them recently? They also need extra water through the hot weather to keep on putting up new fresh leaves. I top dress the Hostas in my daughter's garden with alfalfa pellets in the summer, for a good soil amendment with a boost of nitrogen.
But DO keep the slug bait around them at all times!