Tortoise skin problem?

[Tyanna]

So I still can't tell if this might be his substrate stuck around this area but after a good soak it's still there. Sometimes it seems like he's irritated with that spot because sometimes he will scratch at it and pull his head into his shell. I know the photos aren't great, he didn't want to stay still at ALL. I still can't tell if it's his cypress mulch substrate or something else. It looks kinda stringy? I'm not sure how to explain it. His neck area is what I'm referring to if you can even see anything from the photos. Should I be worried?

 

[wellington]

I can't see anything out of the ordinary.

 

[Tyanna]

Yea it's really hard to see in the photos but I'm probably just worried for nothing. Thank you!

 

[ascott]

Are you referring to the area behind the eyes (ear area?)....

 

[Yellow Turtle01]

There is a small black patch, but it just looks like coloring my russian has one of those on his chin.