Alix2c

So I have a comet goldfish I’ve had for 4 years. He’s in a 55 gal. i noticed recently that his gill only on one side was sticking out.... I don’t see anything on his gills that’s outside of his body but a little white and it doesn’t look like worms or balls or anything. Just like his gill is also white/red. I will attach photos. i have no idea what it could be. Please help bare with me, I can’t get a great picture