Deep Water sps losing tissue. going white

[Chicago]

ok... I have my thoughts but thought I would ask anyways. I have some of my corals.sps smooth skin deep water that are now going white NOT at the base up but random.. tips. middle ect. tissue skin is slothing off. spreading to rest of the coral head. meanwhile others in the tank.. frags and other corals doing fine.

tank numbers are.

1.026
9 dkh
360 calcium
1500 mag
0 nitrate.
0 phosphate


Alk has swung recently from 8 to 10 over a period of a few days. Ph has been kinda low.. but not a huge swing.. 7.90 to 8.10 depending on time of day..

 

[Chicago]

No one?

 

[Aquattro]

pH shouldn't be an issue, nor the alk swing unless the pieces are already stressed. Ca is a bit low, but shouldn't affect tissue. I would suspect pests maybe, perhaps AEFW.
Got pics of the piece(s)?

Assume the obvious is checked. Fish nipping, too much direct flow not an issue, no crabs having lunch..

 

[Chicago]

no .. 40 plus other corals ok.. just hit these two deep water. smooth skin.

no pests to make of.. no fish either bothering it.

 

[Peter Eichler]

Were these maricultured pieces, how long have you had them? Are you using Kent salt?