Fin & Tail Rot or Bullying?!

[PETsMARTchick]

HELP! I had 3 male Delta Tequila Sunrise Guppies in my 15g community tank but one died. His tail and top fin were ragged. Now another one isn't looking so good. His tail is very ragged. The bigger and fancier one doesn't look as bad, is he bullying the smaller one? They seemed to school together, but maybe it was actually bullying. How can I tell the difference between Fin & Tail Rot and nipped fins?

 

[Sasha]

What other fish are in the tank with the guppies?

 

[PETsMARTchick]

I have 5 neon teras and 2 bronze/emerald green cory catfish in the tank with them. But I haven't seen them interacting with the guppies. The bigger guppy just follows the smaller one around a lot.

 

[Barrelchasin]

In my recent terrible experience with fin rot (all my fish have died) all my fish with it had cottony or spider-webby looking strands of white trailing from the areas affected. Their fins got extremely short and they even lost areas of scales on their bodies (white webby material there too). If it is just bullying there will be no white material, just torn off and jagged fins. But then again this is just my experience.