Is Tiersias marbling? He's starting to get a little yellow underneath his chin and I'm really worried that it's from disease since he just got over a bout of velvet, and had a gash in his side from getting stuck in a flower pot :(, plus, he recently got another gash when he jumped out of his cup as I was cleaning his tank and down the drain, but it's healing well :)
As you can see, his chin is definitely darker than now.
I think it may be from stress? I just want to make sure it's nothing serious X]