aww, poor baby. Darkening of the skin can be due to: stress, poor diet, or dehydration (I'm sure there are others also). The humidity should range from 70-80% and the temp should range from a rough estimate of 72-80F, can't remember, I keep mine at 80. They also need a light that gives them rays that the actual sun would so they don't get MBD. Does any of this help?? I mean if you did keep up the humidity, it could have just been something that generated from that. I can only imagine how easy it is for germs to brew in these conditions..