I have four neons in a community tank... with swordtails, gouramis, plecos. Recently I have noticed on 2 of them, what I can only describe as a large cyst/bubble over their mouths. They appear healthy in all other aspects. One of them burst and looks very ragged, the other is still very large. What are these lumps? and should I be worried? I have got some pictures and if I can work out how to post them I will!!!!