I don't know if I'm making something out of nothing here but to me the top of Nitros head looks dry, even when it's wet if that makes sense! I had him on coco coir for his first year and recently switched to fir bark now his bigger. I can't work out if its a bit of residual staining from the coir or if the bark isn't moist enough, my humidity is good 80-90%throughout the enclosure with the humid hide being 99%. It's a closed chamber as well so the humidity doesn't escape during the day.