Originally Posted by
jeep
This looks like a symptom of hex. You're already using metro, but metro works best with high temps and you recently reduced the heat. Since your other fish may not be able to tolerate high heat, I would place it in a hospital tank and increase the temp to 93 for another 10-14 days. Any water changes should be temp matched. You can also add 2TBS salt per 10g during the treatment. You may not see signs of improvement for another week or so after.
There are also some interesting treatments for hex using epsom salts in food or force fed. I'll see if I can find the info.