I've been going through something similar with my beardie. I've been to a vet, and my situation seems to be linked to pickiness and stubbornness, but if you are able to somehow work out a trip to a vet, or even just try an over the phone consultation with one, you should do that! And also make sure all your husbandry is right. In the meantime, you can try what the vet told me; try giving him something new, or even some treats, like fruit, mixed in with his veggies. Apparently some beardies can just get bored of their diets.
Another thing I've been trying is pureeing his food and supplements in a blender, and feeding him with a syringe. I dribble some on his nose, and when he starts lapping it off, I continue squeezing more onto his tongue and he keeps on licking. He seems to like it, and since I added a little water to make it smooth, it's been helping him keep
hydrated as well. Don't use glass syringes if you decide to do this! I made that mistake and this morning he bit off the end and swallowed it! I took him to the vet again right away, and they think he'll just pass it on it's own, but it's something that should definitely be avoided!