The other fish should be fine in the tank with the med,
Read your other post and the behavour he showing are signs of a dying fish.
I don't hold out much hope for him to be honest.
Taken from the link above.
Fin Rot in and of itself is not contagious, but if you keep fish in a community tank you may end up with several fish contracting the infection. This is because the bacteria that cause Fin Rot are opportunistic bacteria - poor water conditions stress fish out, and when fish become stressed, their immune systems become weak. Weak fish are not able to fight off illnesses that healthy fish easily can. So if you have poor water conditions or something else causing stress in the occupants of your tank, you may have an "outbreak" of Fin Rot.
