dragons have wrinkly skin on the sides of their body when they are not filled out. its not a sign of dehydration like it is in mammals. signs of dehydration in beardies are sunky fat stores on the top of the head, sunken in eyes, and hard cahlky yellowish urates. I mean a picture would give me 100% positivity of this but im pretty sure what you are seeing is when your dragon is not puffed up any nor flattened out.