Mine have laid fairly well for about three years than they start to be less reliable for the next couple of years, laying here and there. If they are closer to three years old they won't lay as well. People can lose track of the age of chickens pretty easy, or say they are younger to get someone...
What are you feeding them? Are you sure if their age? Older buffs will lay sporadically like that. What is the size of their coop? Anything around them that would be stressful?