My two gold barbs have had a little bit of white edging their fins lately so I did frequent water changes, added stress coat, and garlic to the water. The one started to get better it seemed. The white stuff went away and he ate and swam normally. The other fish all seem normal. The other gold barb however started hiding in the castle and I didn't really see him eat or come out. Today when I went to check on him, I picked up the castle and he had blood on his side. I have moved him to quarantine and now I really don't know what to do. His tank mates are three other cherry barbs (not usually nippers), two cories, and another gold barb. I feel so terrible because I feel like I haven't been paying as much attention to my fish as I should be :/ so if there is anything I can do at this point please let me know.