fin nippers targeting albino corys

[helen19t]

so I had a problem with a spike in nitrites little bit back. one fish develop fin rot and didn't make and I thought that one of my albino Cory was also suffering from the same thing . but then I noticed even after the levels were dropping and I was doing daily water changes of like 15 the I was still having a problem with some of my albino corys dying. now I'm starting to think maybe it's not for them that I have a fin nipper. and I think I have it narrowed down between a cherry barb and a bleeding heart tetra. I've also noticed that this doesn't seem to affect my green Cory's. I really love chorus so I was wondering if anybody has any advice on what to do to stop the problem, resolve it in some way.