Torch coral shrinking spontaneously then having mouth open

[Rockedash]

My torch coral here has been doing fine ever since i got it around a month ago and then all of a sudden i noticed that it was almost completly shrunk (coudlnt get a photo of that started freakign out). After a minute or two it started to open again but the tentacles were very small and the mouth was wide open as seen in the first photo. I figured that maybe i should just give it some brine shrimp to see if it would help and it looks like it did because in the second one the mouth seemed to have closed. Im just not sure what could have caused this to happen so fast. I struggle with high phostphates around the .90-.50 usually but i think the culprit might be my alk. I tested it at 6 or 7 today the color of the water starterd to change at 6 but when i put 7 drops in it was very yellow. I tested last week as usual for me and everything was fine other then my phosphates which is usual.
My last week Tests:
Alk 9.88
PH 8.2
Phos .90
CA 414
MG 1419
ammonia .1
nitrite .1
nitrite 31
(this was the day before my usualy water change day)
Todays tests:
Alk 6 or 7
ph 8.1
CA 400
Ammonia 0
Phosphates .50 ppm
Nitrates 0
This test ^^^ was done using my own test kit i usually test my own water with my api test kits then go to my lfs to have them test it to make sure its right

A few months ago i went through a really high KH spike and some of my corals like the riccordea in the picture havent really recovered but my other corals minus my duncans and single acan are doing fine which leads me to think it would be a KH issue no because of it being to low.
Not sure how to proceed with things i have the seachem kh booster but im worried that i will mess it up and cause another possible kh spike.
Thank you for all the help and tips and reading through this

 

[Reefing Madness]

BUMP

 

[Alex Cataldo]

It’s the phosphate. Either do a few large water changes or run GFO to get it down to 0.1 I would also try to get the alk under control, typically torch corals are more receptive to unstable alk.

 

[Dave1993]

phosphate high nitrate 0 need nitrate 10-15ppm

 

[Coral Euphoria]

In addition to lowering your phosphate by a whole heck of a lot, your tank is really immature. I strongly recommend you seed your tank with a small piece of live rock from someone's tank and don't buy any corals until you see coralline growing. Also you should consider the source of the torch. Many maricultured torches do bad in our tanks. If you are new to the hobby, better stick with aquacultured pieces for now. Also, get better test kits.