Is my beardie too skinny and dehydrated?

I got my beardie four days ago, he ate normally the past days but he only ate 3 mealworms yesterday and today he doesn’t want to eat anything but he’s been drinking water. He also got some dark marks on his belly and chin. I thought they were normal because he had them since I brought him home is that normal?

I got my beardie four days ago, he ate normally the past days but he only ate 3 mealworms yesterday and today he doesn’t want to eat anything but he’s been drinking water. He also got some dark marks on his belly and chin. I thought they were normal because he had them since I brought him home is that normal?