My bearded dragon keeps getting dark in his tank and having a black beard. His back keeps looking like this and it's at random times. I haven't been able to get his temps right they are either too hot or too cold. I have a 75,100,and a 150 watt that I keep switching and none work. I've tried moving the basking spot higher and lower nothing works. Idk if that's what's upsetting him but what's going on with his back?!? Also this ONLY happens in his tank. When I take him out he is super bright and orange and happy and active. He is eating very well and pooping everyday