Zoanthid not opening fully

[starfishguy869]

Hello, I bought this Zoa frag 2 months ago. Unfortunately, I forgot about it and it fell behind my rocks. Then, 2 weeks laterI found it and managed to save two heads, fast forward to today, and I have one survivor left. This head has tried to open and is showing some of the interior flesh. However, something looks like it is stopping it from opening fully. It has been like that for more than 5 weeks and I am starting to get worried. There are no visible pests and I have never seen asterina starfish munching on it. There is also no film algae on it. I dip it in Revive every week. Can anyone help me with this? It’s supposed to look like this:

 

[Gumbies R Us]

Bumping your post!