That fish has a bacterial infection if you ask me - the white edging on the fins is very typical (you see it called fin rot when it stays at that) and the rough white patches on the body. People may call it a possible case of columnaris but that doesn't really matter. If there was not the white edging on fins it would be up for grabs as to whether its fungal or bacterial (the fact that you've had pop eye in the tank edges it for me as well).
I would consider that aggression plus the stress of the move (they are recent additions correct?) are the chronic causes here, basically weakening the fish to the point where it is that much more vulnerable to opportunistic infection which it might otherwise fight off.
Its best bet is removal to a hospital tank, even a small say 10G set-up (complete with filter, heater. Lights off and put it in a quiet place. Do a couple of daily large (basically 100% per day) water changes. If no improvement within two or three days I would say treat with maracyn or maracyn 2 (antibiotics) as I am quite confident the problem here is bacterial.
If hospital tank is not possible, and you have tried massive water changes daily for a few days, treat the tank with maracyn or maracyn 2 (more expensive obviously). Follow directions carefully - be aware it will damage your good bacteria levels.
Usually you see improvement with these conditions very quickly, if the fish eats and is not stressed and it is not a particularly virulent bacterial strain - like full blown columnaris - that's why a hospital tank is best. Also, if you do not see swift improvement you would be right to consider the risk of other fish in the tank coming down with it - again that's why a hospital or quarantine tank is best all round.
If you try maracyn or maracyn 2 and the fish does not improve within a week, or stops eating, you might be better off euthanising it.
Good luck.
