Hens might stop laying for many reasons: heat, stress, age, illness, nutrition deficiencies....a new rooster would definitely add stress. They might even be hiding eggs because of him.
What age are they? How many do you have? Are they free range? What do you feed?
It sounds like you are doing everything right....maybe a snake could get in and steal eggs? Or it might just be a normal lapse in laying. You may want to check out forums on ' hens not laying' for other ideas. Good luck!