How is the flow in your tank , maybe it is in a dead zone ?
Maybe Turkey baste them a few times a day just too make sure nothing is on them , also sometimes very fine substrate can cause gas exchange to be low and cause low oxygen level so give substrate a stir and make sure your skimmer is running nicely ... wont hurt trying anything and everything possible .
If you can get it off the rock , maybe give it a dip , i usually use reef primer by Polyplab when i see a coral not doing too good ... good luck though and hope it survives