you could try an iodine dip like lugols. i've heard that recommendation before, but i don't know of it's effectiveness. meanwhile, i've only ever seen the brown jelly disease on torches/frogspawns/hammers. i wouldn't worry too much about the bubble. keep the remaining head in a medium to high flow area. if you see more brown jelly, vacuum it out of the tank asap. you can vacuum it right off of the head in question.
jerryatrick has been more successful at saving the remaining coral than i- all the colonies of Euphyllia i had that were effected, are now in the sump, as expensive pieces of live rock.