Help! Xenia in trouble!

[sunce_22]

Here is the problem:

The xenia are losing all of their "little fingers" (the part that pulses) They look like they are slowly growing back, but I can't figure out why this is happening? Can someone please help me! I have no fish in my tank, only a clean up crew. I suspect there is a pistol shrimp in there due to the large amount (hundreds) of baby shrimp swimming around recently. I dont know what is doing this and I dont want my corals hurting.

P.S.

I have had my xenia in my tank for two months. They are always fully extended and pulsing happily. I have checked all the water parameters and they are all safe.