Clownfish mouth open and swollen?

I noticed that my misbar has had his mouth more open the last couple days. It looks whiteish on the inside around the edges. Not sure if this is some kind of disease. I did feed some clams the other day and it cleaned the shell out completely wondering if injured its mouth somehow. It is still eating just wondering if I should QT him and treat with something. btw I just had the light off for a few day because I had a cyano bloom maybe that had something to do with it.