Long Tailed Gold Zebra Danio Fin Issue

[scubaboy1126]

Just bought my fish over the weekend. I got 3 Austrailian Rainbows and 6 long tailed gold zebra danios. They all seem pretty harmonious together and when I got them into the tank the danios seemed to stay together and play with themselves. I did notice Sunday night a couple hours from being in the tank one was getting chased alot by the other danios and I noticed lay night that on was just staying at the top of the tank. This morning when I went to feed them I noticed that one of danios is missing part of its tail gin. So I'm suspecting that it's getting bullied. Is there anything I can do? I read that putting aquarium salt would help promote tail regrowth but I've never used it before and was wondering if the danios and rainbows can handle the aquarium salt. Should I pull that fish out till it gets better or just leave it in and treat it in my tank? Any advice would be much appreciated.

Thank you