Acan STN? Or what?

[Tyguy]

Hey I guys i tried Reddit because it quicker but had little to no luck so I came here

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 ticked 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.

 

[Mr. Mojo Rising]

My acan is on the sand directly under a metal halide pendant, and it gets enough flow that the polyps ripple slightly. This one started as one single polyp. I know most advice says low light low light, but I notice you have zoa's on your top rocks so I have an impression the lights are not that intensified in your tank... I say give it light and watch it grow.