Long tentacle plate dying

[Bluematt1]

Hi I’ve had this plate coral for around a year and tonight noticed some of the tissue has gone on the back and it’s not opening as much

Water parameters
KH 8.4
Calcium 460
Magnesium 1340
Phosphate 0.02
Nitrate a little high at 16ppm

Any ideas on how to try and help bring it back or? I initially thought it just wasn’t coming out but from turning it around found it’s more of a serious matter.
I do have a couple of conch snails that float about cleaning the sand bed or should I maybe move the sand from it’s underside ?
many views welcome

 

[Spare time]

You could try and dip it with something like coral RX.


I will say that your phosphate is quite low (it could be 0 since that would be in range of the error of a lot test kits) but that would cause issues with multiple corals and may not be bad if corals are fed. I just figured I would throw this out there.

You could also put some small flat rock piece underneath it so that conchs don't accidentally climb on it. two littel fishies stax rock is perfect for that if any of your lfs carry it.


Also nitrate at 16 is not very high so I wouldn't worry about that.

 

[Uncle99]

Anybody in your setup which might have tasted him?
But unusual for a quick demise after a year of health when water chemistry is in line.