Hatchery/production quality Buffs should start laying earlier than if you got them from a private breeder of good quality Buffs. Hatchery birds typically start laying around 6-7 months of age, others start around 8-9 months.
ETA: It also depends on what TIME of the year in which they hatched. Late Winter and Spring chicks will typically start laying in the Fall of the same year, while those hatched in the Summer and Fall will typically start laying when the weather warms the following year. So, it makes it seem like they take longer to lay, but their eggs are larger.