Hmm you know what, I think you are right. I had a tiny bit of condensation on the back of the tub before I ever put eggs in it, but when I pulled it out to put eggs in it, there was condensation on all the walls. I'm using HatchRite
Do you have a humidity gauge? Maybe put one in there just to be sure.
If they start dimpling it's not wet/humid enough in there (unless of course they are getting ready to hatch).