What happened to my nem?

[GothFishKeeper]

For a while now my black widow bta has been on the back of my rock structure, right beside the overflow in the left corner but near the bottom of the tank. My clowns haven’t really done anything with it, I’ve just been giving them time to figure it out. Yesterday I turned the flow on both my return pump and my mp10 to see if he would at least come out to a visible location. He did just that, but he’s completely mangled! What could have happened, and is there a way to save him?
Picture is from a top down angle

Nitrates at 2ppm, 0 ammonia

 

[bluemon]

It’s at a point where it is pretty much decomposing and breaking down it seems.

Was it healthy before today?

Do you have any pictures?

 

[GothFishKeeper]

It’s at a point where it is pretty much decomposing and breaking down it seems.

Was it healthy before today?

Do you have any pictures?

Yes it was, this is a screenshot of a video i took on April 25. That’s the most recent I have of it because it moved farther down the back side of my structure like i mentioned. I wondered if the flow was bothering it so that’s why I turned it down yesterday, but it still looked healthy at that point still.

 

[GothFishKeeper]

Update: he seems to have moved to the top of that rock, so he’s alive, but as you can see in very bad shape. Looks like most of his tentacles are missing and he’s just in general torn up. This wouldn’t have anything to do with the watanabei angel (juvenile female) I added last week would it? I thought they were completely reef safe