Thanks for all the responses. I was skeptical about it being Ich too. I've been monitoring this guy very closely the past couple days. It does resemble gravel or something like that. I'd rather not try and catch him and stress him out too much. None of my other fish have any signs of illness.
As far as food goes, he's eating seaweed sheets, spectrum, LRS and seaweed extreme alternating days. So I think his diet has been fairly regulated.
All my parameters in tank are on track as well.
I'll keep him under close observation and take this fungal idea into consideration for sure.
What type of treatment is recommended for fungal?