what are these gray marks under his mouth

[beardy27]

This afternoon I noticed these strange gray marks between his scales around the lower part of his mouth and jaw. I did not notice them there this morning. Is this normal or should I be worried.

 

[CooperDragon]

Is it food? If you wipe the area with a damp cloth does it rub clean?

 

[beardy27]

Is it food? If you wipe the area with a damp cloth does it rub clean?

Nope, that's the first thing I tried. I then used a soft bristled toothbrush and rubbed it with water and nothing. He is inside his hide sleeping now and don't want to bother him so I'll see how it looks in the morning. The only other thing worth mentioning is that he is on meds for parasites, panacur is one of them and I administer it with a siringe which does get messy around his mouth.

 

[CooperDragon]

It's possibly natural dark coloring but my first guess was food because it appeared so suddenly. It doesn't look harmful to me though.