Palythoa heads closing?

[Reef Knub]

Hey all - looking for some input on what may be potentially going on with my palythoa pictured here.

Over the last month and a half I've noticed two clusters of heads closing and staying closed. It's also starting to spread, but happening so slowly.

Tank parameters have generally been stable, see current parameters below. The only dip was PH and salinity which had dipped to 7.8 and 1.023, three weeks back. I've been dosing eight four to slowly bring that back up.

Given it's localized to those two spots on the palythoa rock, my guess is it's something else and not water parameters, but can't tell what's going on.

Any thoughts??
Thanks!

Salinity 1.025
PH 8.0
Alkalinity (KH) 140 ppm
Calcium (GH) 422 ppm
Magnesium (Mg) 1450 ppm
Ammonia (NH3) 0 ppm
Nitrite (NO2) 0 ppm
Nitrate (NO3) 1 ppm
Phosphate (PO4) 0.3 ppm

 

[threebuoys]

Looks like you have a couple of fish that are often called "reef safe with caution"

Possibility one of them may be nipping at the coral when you aren't looking. I had that happen once with my bi-color angel. Once I removed him, the soft corals responded favorably.