Again you are asking about multiple species in the chicken forum......they all have slightly to very different habits and needs.
If your chickens are about 18 months old, there's a very good chance that they are molting or getting ready to molt.
If you free range your chickens there's also a chance that they are laying out in the range area.
If your chickens are confined and don't have enough space, that stress can also cause laying to stop.
You need to provide details on ages, housing, population numbers, and feed separately for each of these species in order to obtain viable answers.