Is this the first time it has done this in how many months of owning? Sometimes they completely deflate to expel waste products, as their food intake and waste outflow is the same "mouth." Do you feed it? Usually the sign of an anemone dying is you get breaks or tears in the foot, and stringy tissue starts coming out.
Okay I don’t see any tissue or tears in the foot, but maybe he was stress while I’m cleaning cause of water movements and rocks movements and some floating dirty stuffs, was done cleaning it and he’s still like that maybe wait until later? Yeah I feed him once yesterday, bought him 4 days ago