What's going on with my leather?

[Aumming]

It's a neon toadstool leather. I've had it for about 2 months now and it was doing fantastic. 2 weeks ago its polyps stopped extending and it shed. After shedding, polys extended for a day and then this started to occur on the surface. It's a crusty white starting to cover it. I have another toadstool leather in the tank at similar light levels and it is showing no problems.

Stats:
PH: 8.4
Temp: 77-78
Salinity: 1.025
Ammonia: 0
Nitrates: ~15
Nitrites: 0
Calcium: 350
Phosphates: .9 (on the way down, I'm running both a refugium and phosguard in a reactor)
Alk: 12

 

[Webslinger]

They will do this. It should come back better after it sheds.