They actually have what I consider a pretty dry environment; their run has a roof on it to keep rain and snow out as much as possible. We are now well into winter so everything is snow covered and frozen but the girls are still able to dust bathe in part of the run as the dirt never got wet and frozen. Their coop I clean out once a week. It is also dry, the only thing that makes it wet now is I swapped out my ordinary heated waterer for a heated nipple waterer about 3 weeks ago to keep the water from getting so dirty so quickly from their beaks or shavings getting flung into it and since doing that when the girls use the nipples it drips and then freezes on the stones I have below it. I’m going to be chipping them off tomorrow when I clean the coop. I don’t think that could be it though? I don’t see any mold in the coop either