I had the same issue with my first clutch. Cling Wrap did the trick - my humidity immediately went from 70% to 98% in the egg tub. I'm using Press-N-Seal on my other eggs, and it seems to be working just as well. My first eggs never fully recovered from their dimpling (day 24 now), but they do look better. I'd suggest just making sure you have a digital hygrometer in the egg tub so you know exactly what that humidity is doing.