Yea sounds like mold and that is bad news. I know allot of ppl on here use aspen and have pretty good experience with that. We have NO humidity here in AZ so we would mist once a day. But when they went blue and it was time to shed we would add a moist moss hide. We would also try to foil the top of the screen part of the cage and you can also take a wet wash cloth and put it on top of the hot hide. All of these things assisted us in having perfect sheds. Good luck!