this would most likely get more responses in the coral care section but as for your problem at hand if it falls apert its dead.many time with xania it goes through stages that it will not pulse or open up..if everything in your water tests good but the phosphates try adding a phosphate remover I recommend Roaphos (not sure if i spelt that corectly) but thats how it sounds.this is a mineral type product that removes phospates from the water but will not leach it back in when it becomes full to its holding capacity(removal)this is one of the more expencive products but works very well.. has anything else changed in your tank? such as placement of powerheads? hows your alk and cal ,ph levels ect.are you checking mag?sg all of these things can effect the xania if off kilter in levels.however xania has been known to grow wonderfully for long periods of time and just dissapear overnite.good luck