Hi, I have a green one, and looking at the foot in that last pic it doesn't look too healthy. I think it will be a gonner in a couple of days so keep an eye on it, if it's starts to look any worse cut your losses and take it out before it does any damage.
If you can try to place it in a hole on the sand so it can sink it's foot in. It might recover but as I said it doesn't look good.
I feed mine one silverside a week, and it's about 12" across now.