Brown stuff around gills and fins

[Eclyps19]

I just noticed my magnificent foxface has some brown “gunk” around his gills and on the fins closest to the gills. Behavior is 100% normal, eating fine, nothing unusual. It just looks kinda gross and wanted to see what it might be. It’s on both sides, which seems weird to me. Could it be related to the food that I’m feeding, which is this week a slurry of mushed up pellet food, mysis, and vitamins? It looks about the same color.

 

[Eclyps19]

Well then! A few hours later and it’s all gone. Who knows what that was, but I’m not concerned anymore!