Zoa colony suddenly closed, one umbrella'd?

[Stomatopods17]

Very sorry for the poor quality image, my phone doesn't do blue lighting well, but basically all the polyps are closed, except for one polyp that's in an umbrella state (on the right).

Light: 2x AI prime 10" above water surface (colony is about 12 inches below water surface), 29 gallon standard. I just turned on acclimation mode yesterday (80% normal intensity) to see if maybe they suddenly hate the light and no results yet.
Salinity: 1.026
Ammonia: 0
Nitrite: 0
Nitrate: reading 0 but have dino growth
DKH: 12
PH: 8.1
Calc: 400
Phospates: don't actually know, no test on me atm. I have a sump on this tank with a skimmer and the skimmer hasn't produced much waste even have leaving it off for two weeks, I just turned it back on yesterday and there's nothing in the cup. (left it off cause I was gluing new frags).
Temp: 79, just turned down the heater this morning.

Feeding: reefroids+mysis mixed in tankwater weekly, I feed the tankmates large krill (mantis shrimp+damsel, they do not bother the coral)

History: had this coral for a few months actually, it was open, bright, actually the coral always first to open and did really well from the start. However in a few days ago I noticed the colony doing this and it hasn't changed at all. All the other zoanthids are doing great in the tank, multiplying infact. I did dust it off to see if maybe it was a debris issue, but nothing. I dipped every other new coral I added to the tank, so I don't believe pathogens got in. There's no algae growth on or around the coral and I blow any off that's around it.

Not sure what to do, everything else is doing great. I tried researching umbrella syndrome but its only 1 polyp doing it, the rest of the colony is just closed. Is this normal? Really don't want to lose this colony, its done so well and tbh I can't ID or find a match anywhere for it (and the photo doesn't help with that here.. I THINK they're either candy apple reds or oompa loompas.)

 

[LiLinka]

I would definitely test your phopshates, what are you using to test your nitrates?

 

[Stomatopods17]

I would definitely test your phopshates, what are you using to test your nitrates?

I use API brand for testing, refractometer for salinity.

I think both would be 0 either way because dinos are starting, I'm wondering if I should try a 3 day blackout with an auto feeder to try and raise the nutrients a bit, but idk if that'd do more harm for this coral.

 

[SimonMo]

From my experience some zoanthid polyps even if they are growing very well when you are e.g. cleaning the frag, all the colony closes but few of them can't close and have this umbrella shape. In diffrent day if I am doing the same thing, totally other polyps won't close. This is strange, but i wouldn't be happy and i would treat this polyp as closed, which is obviously bad syndrome for colony. I can only guess that this polyp is full of food and that's why he can't close.

 

[Stomatopods17]

Coral's been dead for at least a week now.

Attempted to dip it, then attempted to keep it in another system, never opened and melted away. All the other zoanthids are still perfectly fine but I noticed my fire and ice zoas were closed for a week, then I moved the powerhead and its fully open and perfectly fine again. I also now have little shop of horror zoas that are doing good too.

I would blame the powerhead for the candy apples (what I think it was) but I had it unplugged majority of that time.

 

[Aaron1222]

Coral's been dead for at least a week now.

Attempted to dip it, then attempted to keep it in another system, never opened and melted away. All the other zoanthids are still perfectly fine but I noticed my fire and ice zoas were closed for a week, then I moved the powerhead and its fully open and perfectly fine again. I also now have little shop of horror zoas that are doing good too.

I would blame the powerhead for the candy apples (what I think it was) but I had it unplugged majority of that time.

one thing i would do is send out an ICP test, i had colonies of zoas closing up for week and weeks on end, starting to melt away, then i sent out an ICP test only to see that my iodine levels were low, so were my strontium levels, i ordered some triton labs iodine and strontium, started dosing weekly, and now all zoas are opened up, and even some of the ones i thought had melted away, have polyps grown back and opened wide! i definitely recommend looking into it!