20 one year old chickens aren't laying!! Help!!

[hamiltonfarm]

What am I doing wrong? I have 20 hens that have just turned one. A few of them started laying in October but stopped at the end of December. Why am I not getting any eggs? There has been 3 roosters living among them but I am getting rid of two of them. They are on laying feed and oyster shells. They did not molt this winter because I kept 14-16 hours of light in their coop. Help please. I want eggs

 

[Odelia]

What breed of chickens? Are you really getting no eggs at all? Are they free range or are they kept in a coop/run if so how large is it? Do you have any predators tormenting them? For example a dog on the other side of the fence from them.