pima fix is my best friend in my department. It cured massive fin and tail rot, along with bod slime that occurs from the stress of being shipped in. If all esle fails, drain half of the water from the tank, and fill it back up with fresh water. Add jthe reccomended dose of cycle and aquaplus.

I would also get the water tested, it sounds like yoru fish might be poisoned from something ( besides the mouse). Make sure you arent over medicating. A good indicaions is the fish are at or near the water surface gasping for air. Some become lathargic, some get the shimmies, and some jsut upad die.