Help! Skinny Mourning Gecko!

I was moving my mourning geckos into their new enclosure today and found one walking around on the ground. He was WAY too easy to catch and when I looked closely, I saw he had severely depleted calcium sacks and generally was just incredibly thin.

Just a few months ago, he was the biggest of the group, even after an incident with his tail getting caught in the glass door crook.

There doesn't seem to be NEAR the information available on these as there is on frogs, or other geckos. I was wondering if anyone could give some some advise to get him back up and running.

They generally eat gutloaded crickets, repashy crested gecko and I keep a dish of ground up cuttlebone in their tank. As you can see in the pictures, the rest are fine... and he is not.

Any help would be much appreciated!

actually its a she because mourning geckos are all female try feeding it food by pressing the food（decapticated worm/fruit mix） at her mouth