Please help.

Hello. So I’ve had my axolotl for a year. He came to me as an adult. He started growing a red mass on his gill. I did research and everyone that I read said it’s okay and to just make sure the water is clean. So I let it be. But now, it seems that the surrounding gills are shrinking. especially the one directly next to him. The woman that I got him from recommended methylene blue baths. The water is the color of the blue on the API testing kit. I’ve been switching him from medication to normal water every 12 hours. I feel like it looks slightly worse after rubbing him but i’m not sure what to do. You can’t see it in the photo but more tiny red dots are popping up. He is eating and active