Here lately my beardie seems to be eating his crickets a little slower he still eats the 15 per feeding but he just seems to be eating them slower and he doesn't seem to be eating his greens as much. Could this be that the crickets are to big for him (they are not bigger then between his eyes but they are probably the biggest he has been getting). Or is he going to start the swap from wanting crickets and wanting more greens?
It could be "spring fever" as well, if he has hyperactive behaviour!
Or as you said he's changing his diet, I guess if he's still happy and healthy there's no need to worry for now. But I don't know. I did worry when in the same situation and took mine to the vet, just to be told she was healthy and slowing down because of spring hormones.