three chickens won't lay eggs

[keyah]

I have 4 hens. three are about 4 yr old and one new one is only one yr old. the new one lays every other day. the older chickens haven't produced an egg in a year. Are they too old? they are big and healthy and have lots of room.

 

[enola]

It is time for some new hens. They are either on strike, retired or on vacation. . . . .

 

[Buster]

Do they have light for 14 hours a day? That can kick start them. A couple weeks of light and they should start laying again.