Sick scoly coral

[CamGG]

I'm fairly new to the forum so apologies if I posted in the wrong location or my format is wrong.

I've had this coral for many years now and it's always thrived. This hole formed abruptly one day a few days ago and now it seems like another one is starting. It's tissue is also shrunk. It'll still eat but very slowly. When the hole first formed it seemed like sand was inside of it and I gently blew it out with a turkey baster without touching the coral.
My water chemistry
Nitrates ~20 this is actually lower than normal for my tank though I know it's still high
Nitrite/ammonia 0
Alk 9.5
Calcium 500
pH 8.2
Temp 79-81

I haven't added any new creatures or live rock to the tank in years so if it is a pest I don't know why it'd come all of a sudden. I've been doing weekly 20% water changes to try to bring my nitrates down. I replaced all my RO filters recently but TDS 0 and everything else in the tank is very happy.

I'll appreciate any help. I've had this coral for so many years and don't want to lose it.

 

[blaxsun]

Just out of curiosity, what's your magnesium at?

 

[CamGG]

Just out of curiosity, what's your magnesium at?

I'm not sure unfortunately. I don't have a magnesium test kit. I have a very understocked 90 gallon and don't dose it. I've been doing weekly 20% WC with instant ocean. I can't imagine it'd be low but if high can be an issue I'll buy a test kit while I'm desperately looking for some DipX

 

[vetteguy53081]

Calcium elevated (400-440) and may be affecting alk. These coral prefer moderate light and water flow and if any changes can fcause effect. Overall, the coral looks good,
Assure salinity and temp has not become elevated

 

[CamGG]

Calcium elevated (400-440) and may be affecting alk. These coral prefer moderate light and water flow and if any changes can fcause effect. Overall, the coral looks good,
Assure salinity and temp has not become elevated

I double checked my alkalinity and it's 9.5. There's a good six or more mouths on this guy. I don't know their anatomy. Is it possible for one "node" to die? A new hole is forming right above where the first one is. Someone pointed out in another forum that the tissue looks otherwise healthy even though it's splitting.

 

[IKD]

Has your temperature typically been this high? I find my scoly’s stress at temps over 78 and prefer 76-77.
That said, you said your scoly has 6 or more mouths? Is this a scoly or possibly a trachyphyllia?

 

[CamGG]

Has your temperature typically been this high? I find my scoly’s stress at temps over 78 and prefer 76-77.
That said, you said your scoly has 6 or more mouths? Is this a scoly or possibly a trachyphyllia?

That's been my temp for the at least 5 years I've owned it. I double checked my temp control with a very accurate thermometer. After even more research I believe it's actually a parascolymia rowleyensis. Literature on it is very sparse.