I've been finding basil leaves that look like they've been nibbled on. A worm perhaps or an earwig. I'll have to go out some night with a flashlight and take a closer look. Only a few leaves though and they've been like this for a while now. A couple of weeks ago it was celery. One of my plants had all of its new growth eaten to a nub. I suspect a worm of some sort in that case. It was just the one plant and after I discovered it new growth returned to the plant and I haven't seen any damage to the celery since.