Pies, I have Xenia that is so big and growing so fast I can hardly control it. I have just had a sick one which will come right shortly. It got stung by my Heliofungia, (So did I for that matter!).
Try getting a bottle of "Ecosystem, reef food liquid", (The same people who make miracle mud. (Ask Reef).
Or real quick go and get some general coral food and dose it quick.
Are you using coral food?
Another good one is REEF SUCCESS Coral Food.
I am running colourful acros in my tank also now, so my water is good.
Nitrates 3
Po4 0
And my Xenia is pumping.
Craig