I had the same problem, and didn't realize what was going on till it had shrunk a lot. And a peppermint shrimp that would steal all its food. I stuck a clear cup over it with live brine shrimp in it. They come out with the smell of food, and a couple weeks of daily brine shrimp treatment the tentacles were getting bigger. Then something larger, like mysis. They can live for a very long time without food. I finally got sick of fighting my peps over the food and let it go, and it had color/tissue for months before it was gone.