I have tried getting pictures of it so that it would be more obvious what I am talking about but I was not able to get any good pictures.
I do not know if torn is the right word to describe the damage to the tail. The tail is not missing any pieces, which I would think would be the case if they were being nipped by I could be wrong. Instead, it almost looks like the area between the spines in the tail fin has disappeared, just leaving the spines themselves. However, I can't say for sure whether or not the fin between the spines is gone because the tail is clear and I have not been able to tell for sure.
Also, when I woke up today and went to check on the fish, I could not find any sign of it. I did not have too long to look for it so it could still be there but I didn't see it anywhere. I am going to look some more when I get home. I know that it is possible that the other fish ate it, but would the entire thing really be gone in approximately 8 hours? Also, if the other fish did eat it, wouldn't that be unusual as these are all supposed to be tropical community fish and everything I read seems to suggest that they should coexist with each other?
Finally, if nipping is the problem, what can I do to help protect the other fish. I have some caves and plants on the bottom of the tank and then I have some other plants and cover near the waterline, so it seems like there should be plenty of places to get cover.