I have had this pink spotted diamond goby for about 4 months and all of a sudden it stopped eating a few days ago and is not as active and hiding. I do see him still occasionally sifting sand, but he typically eats a lot when I feed the tank and won’t touch anything. There is no labored breathing that I can tell. I see no visible signs of disease and all other fish are acting normally. No new additions in over 2 months. Does anyone know what could be wrong?