Sorry. I know it can be disconcerting but patience and a thorough process of eliminationn to discover possible cause(s). So many possibilities. i.e. the breed of chickens, new enironment, changes in diet or weather, illness or other stress related symptoms. Is it possible they are laying somewhere else if permitted to free range? If confined, could prey or rats, or even the chickens be eating the eggs. More than likely it's the change in seasonal weather with winter coming soon and chickens naturally lay less than more. How long have they been on strike? How old are the hens?