Where did you get your RIRs? My RIR, which came from McMurray Hatchery, started laying at about 5 months of age. But the start of laying varies from bird to bird, so I wouldn't worry about yours not laying yet. Patience is one skill that raising chickens teaches you...I have 3 RIR and they are over 6m old and still are not laying. Are these a breed that need more time to mature as I am ever so patient for then to lay.
They are eating laying pellets and scratch and good greens. So what's up?