I agree with Christy - could be a vitamin A toxicity. Are you supplementing with vitamins that contain any amount of vitamin A?
Mustard greens contain 53 IU/g of vit. A and dandelion greens contain 140 IU/g!!! That's more than twice the amount that spinach has. Spinach only has 67 IU/g. But it's the high oxalate content in the spinach that makes it so counteractive with beardies. Oxalates bind calcium and make it usless in their body.
I would suggest keeping the mustard greens on the menu and replacing the dandelion greens with collard greens. You can still give dandelion greens occasionally, if he really likes them. This should really lower the vitamin A content in his diet. Also, collard greens have a very high calcium content (14.5:1 calcium to phosphorus ratio).
I've never seen what a vitamin A toxicity looks like, but all of your beardies look healthy to me. Other signs of vit. A toxicity are bloating of the body and lethargy. Don't mistake laziness for lethargy. A reptile who has recently eaten, or is entering the pre-shed stage, or got up on the wrong side of the cage, will still be alert to his surroundings, responsive to stimuli such as loud noises, touch, and pain. A lethargic reptile will not.
Good luck and keep us posted.
Veronica
Beautiful Dragons