First of all, I would check the temp of his tank. If it is oddly high or low get that fixed immediately. If he is showing the behavioral signs that he is stressed that could be causing the blackness.Hi every one, this is my Duggie, for months now he has had the blackness under his scales on his chin it stays their and doesn’t fade, it also looks like one of his spikes is hanging if or having in grow underneath. Does any one know what this may be?