Has he been pooping regularly? It looks like you either have him on crushed walnut shells (desert blend) or sand, which either are highly not reccomended and could cause impaction and other health issues. They lick and taste everything, and when they are going for their prey they get in in their mouth and end up eating it. Petstores will reccomend it, but try to Google walnut shells and calci sand on young dragons, its almost never a good thing. Something solid, like reptile carpet, papertowels, tile, non adhesive shelf liner are all good substrates that have no risks.
And my female is 5 months and 11" and eats between 30-40 crickets a day with some super worms and dubia roaches (another thing you can try, mine goes CRAZY over dubia) so it may be something to worry about. Even if he doesnt get impacted from the substrate, just a little can cause him a belly ache which may be why hes reluctant to eat. And if he eats wax worms, he will probably eat repti worms, they are very similar. You could also try butterworms, aparently they smell like fruit to beardies and they love them, or silk worms. Theres lots of feeders you can try, Im sure he will like at least one of them