Yeah birdsnests are a pain that way, I'd just leave the main colony intact, maybe frag a large piece off if you can. Its hard to say how crabby it is about the whole thing and whether the tissue necrosis will continue or whether it will just stay as it is. Its kind of a crap shoot really. If you're totally in love with it, frag a chunk off but if you can get another piece or are indifferent, just wait and see
