agreed. tattered fins and tail.
i dont recall major quarrels b/n themselves to cause such wound but again never kept 6 in 20G..
Do you have any kanamycin avail? If not, bacitracin ointment?
Can you isolate it w/in 20 G Q/T by using large clear jar (carbon jar but punch many holes for circulation). Punch good amount of holes 2/3 way around the jar. 1/3 without the holes will be the bottom.
Lay the jar down on the side with some gravel to hold the jar down. Punch one hole on the lid and stick air line tubing thru hole . Attach small coarse air stone inside the jar. As bubbles leave thru some holes, water will circulate thru jar.
It may heal itself or it could develop further complications.
Being wild cats, I would medicate ASAP .
This couldve been due to shipping as well. Pretty Common actually, Looks great when arrived but develops problems within days.
Keep us posted.