Could be anything. But a spray with Garlic Spray will probably get rid of the culprits.

Neem oil works well and lasts about 10 days each spray if you apply during the damages. Leaf miners, caterpillers, and slugs can all do these things. It may help to provide a photo of the damages too. Garlic spray can harm some tender herb leaves, and is also used as a mix in some weed killers! Japanese beetes are in full force now, so they can attack easily too.