Pulsating Xenia is it dead or coming back

[CAN_REEF]

Hello I am new to SW and running 55g saltwater tank for past two months and all parameters are fine have some live rock and my dead rock is turning live some green zoas are doing good. 2 weeks ago I bought big pulsating Xenia with 8 branches lost all branches after a week and now it looks like this with white skin like substance growing on the left over part please let me know if it's coming back or not.

 

[Seyoz]

Is that by where you top off?
Or the return feed line from sump/Uniquarium?

If your adding top off to sump and that's where your return sprays, the salinity and pH melted by drop when topped off

 

[Seyoz]

If HOB, siphon tank water into Buffered Top off water in bucket.

Slowly cup in. Put hand on surface so doesn't mix on corals, doesn't splash and gives it little more time to mix better..