How long until you get concerned…

[trsmith18]

Is it a sarcophyton or a discosoma, rhodactis? If a “leather” then give it time. What’s the system conditions? That contributes

Sarcophyton.

 

[Tamberav]

I would not be worried, they can close for days and weeks (when ticked). They basically do so every time they shed as well.

It isn't dead till its disintegrating and if only one part looks bad, you can just frag that part off.

 

[trsmith18]

Pic is worth 1k words.