Do you only feed them crickets? There's a chance he may have gotten bored of them. Try adding roaches, mealworms, and the occasional pinky mouse into their diet. Make sure you always properly dust their food, as I've found amphibians with MBD can sometimes struggle to eat.

While I do recommend taking him to a vet, I know that can be hard for some people. Parasites and other illnesses and cause frogs to not eat. You may have to end up force feeding, but that is only if he is extremely thin and won't make it much longer without food.

Keep us posted on what happens!