The screen on my phone is busted so hard to tell, but looks to me like poo.
I would give him a warm bath and use a soft toothbrush to see if it washes off. Be careful of water temp, dont burn of freeze him
I just set Swordtail's timer for his bath and paused it so I could actually fill his soaking bowl up and he crawled over my phone and canceled the timer
Mirage came out of brumation on April 26. He was doing great. On May 2 he started acting funny. We just redid his tank, and he keeps going into one of his hides. He just lays there. He shows no intrest in food. HELP!