My goby seems to be having some skin issues and I am having trouble finding answers on Google a few days ago, he developed a discolored area behind his head. It's kind of beige in color. He turned white a day later, so I thought it was just a color change, but his yellow came back super vibrant--except for the beige spot. He is acting like he is uncomfortable and scratching himself on the sand. He is still coming out to eat, though he has been doing more open swimming.. Over the past week, the beige coloration has been spreading. His top fin also seems to be rotting a bit now. I have some pics below. Any help would be greatly appreciated!!!