Leaves look chewed on... But no bugs.

Ive never seen this before, and it's only on a few of my girls. Some of the leaves on new growth look as if they have been chewed on, but there are NO bugs. I have looked over them very very closely... Nothing, and it's only on a few of the plants. There have even been entire leaf blades that look as if they have been chewed off. Otherwise, they look great. It doesn't seem to be affecting the overall health of the plants, so I'm not that concerned. I just keep seeing it though. Any ideas? Maybe it's humidity? It's very dry here so I need to run a hunidifier 24/7 just to keep it up to 45-50%. Sometimes it runs dry before I catch it so the humidity will drop to 20-25%... Could this swing in humidity be causing it? Temps are consistent at 75-77F day, 65-68F night.

Did you ever figure anything out??

Naw, Im gonna guess it was maybe ph or something who knows lol. About 3 weeks to harvest now and looking great.