Walnut shell substrate. Zan is kept outdoors, so keeps up humidity well in FL. Humidity is usually always above 50% in there at all times, even in the midday when the temps are at their highest. It's hard to get a good pic when he keeps moving:)
:Hey girl, I am glad you are concerned, I can't tell from that pic, if you can take a better pic that would help, but it could definitly be scale rot... I hope not. What do you use for substrate, and how do you keep up the humidity?