Those are Darth Mauls, got them from Aqua SD and they grow like crazy. Started off with 2 heads and now there is at least 13 and it has only been a couple of months.
that happens... you're supposed to keep them at about 12 polyp frags... when they get big, split them up... once you have more than a dozen on a plug they'll all melt away... the only way i know you can have alot of them is if they're on like a branchy rock... or on a sand mat... that way the foot or the polyp themselves won't touch and melt away with eachother...