Anytime fish are behaving unusual I check amonia, nitrites and nitrates and make sure the heater is working (mine recently was not workingalso after 1 1/2 yrs even though the light came on. Good thing I also check thermometer). Then I do a water change siphoning the gravel.
This fish may be more sensitive and be the first to react if there is something elevated. Doesn't look like anything to me and eating is always a good sign.