The hens could actually have a problem with stress. Yes, chicken can be stressed out as well! A stressed chicken will not lay eggs. There might be a predator lurking around, getting all the hens alerted and scared. Be sure to have the coop cleared of any holes, small animals, like rat and snakes, could squeeze through and have their buffet. The mere presence of a larger predator, such as foxes, or a barking dog, could worry the lot enough to halt production. Keep the coop a safe, conducive place for them to stay, just like how you want to feel at home while you are minding your business. Naturally, if the mother finds that the environment is too dangerous, she will avoid laying her soon-to-be chicks until it feels safe enough.
Continuing on stress, overcrowding is another reason on why they could start getting unruly. If they are closely packed, they might start pecking each other and that creates more stress. Plus, the chickens might hurt each other, with untreated injury leading to a coop wide infection. Give them ample of space to move around, bigger is better, but a minimum of 3 square feet is a must. Keep them stress-free and you get your eggs. Remember, a happy worker is a productive worker.