The blistering certainly looks like edema, to me.

I can't quite tell by the picture, but it looks like it could possibly be aphids???

Thanks. I'd never heard of edema before but I just looked it up and that kinda looks like the same same thing. So basically overwatering? Could be. I probably got too lazy with watering a whole flat and forgetting to check that it didn't all get absorbed one time. They looked just fine a week earlier.

I up-transplanted them all to 4" pots, and I'll see if they come out of it. I turned a fan on for a more direct breeze in my grow rack too to keep the tops drier and hoping to fend off fungus growth.

I don't think it's aphids or any pest. Not seeing any signs of pests in my grow rack (yet).