I had 2 hammers. Lost one exactly like you describe with this hammer. Same species too.
Last 2-3 weeks my neon green hammer has been receding . I don’t know why as other corals is fine . I check params almost daily .
I thought it was pooping but something else is wrong. I posted a picture not too long ago where I see it’s mouth protruding very evidently
It’s still in my system receding daily. My favorite coral too.
I can dip it , but just don’t know if it’s going to make it
Now , I’m afraid to get another euphullia