I have some holes too I'm thinking they're 35 days old the ffof has been water twice and their wanting to be fed I'm going with a half of a dose of Advance Nutrients cause the plants are small but they should handle a half dose cause the they handled the ffof then water next time and a full dose the time after that
Man mine were getting ate up like that a little at a time and I found a stinkbug in there. That's what was causing my holes. They were bad in the southeast this year, freaking everywhere!
Looks like a bug had a bit of a THC hit there, plant won't be bothered one bit. It happens, I sometimes see a leaf here and there with a bit missing but no bugs. I hang those yellow glue traps around the grow room to catch any flying insects and also lay a couple between pots to catch crawlers.
Unless you see a fair few leaves like this I wouldn't be too bothered. If I was an insect I'd take a few bites out of your great looking plants too