My beardie eats when he wants to eat. When in brumation he'll go weeks without eating. Just make sure you always put some food in there no matter what. If he won't eat live foods make sure you dust his veggies with a calcium powder every couple days and multi/D3 supplement twice a week.
You really shouldn't feed your dragon lettuce. There is no nutritional value and its really just water and fiber. Stick to collared or turnip greens. I linked you a caresheet that will explain what you should be feeding. Its nice because it is color coded.
Nutrition Content