Head/Tail Light Tetra ?

[normd]

I have four of them. The two larger ones have some sort of growth on the tip of thier bottom lip. Looks almost like a tooth to me. Just these two have them. It doesnt seem to affect them or the others at all. Just what is it?

 

[b4au]

I think one of my head and tail lights had it also. Is is black? Mine had it and then it looked like it kept getting darker and darker so I put it to sleep. I couldn't find anything that said what it could have been. I looked through my fish book but it did not sound like any of the problems the book listed. My fish seemed to be perfictly fine also. it ate and everything. Let me know if you figure out what it is.