It sounds like yours are on a healthy diet ! Do you feed them any bran or oatmeal ?
It's illegal to breed + sell locusts in the U.S. so American beardie owners like myself don't have experience with them but crickets would be the closest thing. I kept mine on a small layer of bran or oats and usually gave them carrot, potato, sweet potato. I didn't give them much in the way of greens, their droppings would get mushy.