Need help with my Sarcophyton leather coral

Hi everyone! I’m looking for some advice about my Sarcophyton leather coral.

It hasn’t opened or extended its polyps for about a month. The coral is still soft to the touch and moves naturally with the water flow, but green patches that look like algae are starting to grow on its surface.

I’ve noticed that a film forms on the top of the coral. I gently removed it once, but it seems to be forming again.

All my other corals nearby are doing well, but this Sarcophyton still hasn’t opened.

Has anyone experienced something similar? What could be causing this, and what would you recommend I do to help it recover?

Any advice would be greatly appreciated. Thank you!