= Partial Water Change
I suggest a 50% PWC
daily, with fresh treated temperature matched water, to keep the water as clean as possible. Keep a look out for any signs of the condition worsening. If it does get worse you may need to treat with meds. Which meds I'm not sure of but someone here will know if it comes to that.
Are there any other tank mates that may have caused it? Any sharp decorations or rocks?