Acan STN? Looking for help and tips

[Tyguy]

so in early march I got this 2 head candy can acan, I put the coral on my frag rack closer to the top of the tank (shown in photos) withen probably 2-3 weeks I noticed it was not looking the best but not to bad so I did some research and learned its more of a lower tank coral and lower flow coral, because of this I moved it lower on to the rock shown, after a week I noticed some tissue recessing and figured I just pissed it off and left it but 3 weeks later I noticed more exposed skeleton and took photos in case i needed them later (last 3 photos) come to now I’ve noticed it seems to have gotten very slowly worse so I came here, it’s later in the day 7:30 pm so it’s closed up more then during the day and definitely opens up more during the day. Im assuming this is STN? I’m unsure, what do you think?

also the aenomone never moves and stays in his spot happily (thank god) and the Prada cup below dose sometimes send out sweeper tenticals but none have ever reached the acan.

 

[Ultimate Corals]

You have a couple things going on. Your alk is low compared to your cal and mag. I'd look to bring that closer to 8-9. Your phosphates are a little high. I shoot for .1 - .15 .Your temp is running a little warm. Especially for acans. They are usually collected in less then 71 degree water. Too warm speeds up their metabolism and they basically starve to death. Next is your inverts. Hermit crabs, bumblebee snails, urchins, peppermint shrimp can all nip at corals. Lastly your tank looks very BRIGHT. More light isn't always a good thing.

Those are a couple things I would look into correcting