dark spots

Hi guys! So I have had four beardies and this is the first time I have seen this - Sully will randomly turn only a few scales in his beard black. Both times he was being put back in his tank after napping outside of it, so he definitely could have been startled. But I've never seen only a few...

I have a I have a 1+ year old male bearded dragon pictured below. A few weeks ago, I noticed that he had some dark clusters of scales on his chin that were not before which seemingly appeared without explanation. I tried brushing them off with a toothbrush, (which obviously did not work) and I...