WHat kinda light is on it, and what kinda water flow? Weird coral. Some with great tanks can't keep it and never seem to know why. But, like said already - you'll know soon.
How many times did you do that KH
test? Not that I know if it has anything to do with your xenia's currently poor health. With the dip sticks saying something so different, I'd at least check twice.
BTW, know what kinda xenia - elongata (brownish streaked leaves) or pom pom (white/silvery looking)?