Why have they stopped laying?

[Kyng]

I also just realized you said some went broody and haven't laid since then. If the weather turned after they finished raising their chicks that could also explain why they didn't start laying after being broody.

Didn’t raise any chicks, just went broody. But makes sense.

 

[Ridgerunner]

You have gotten some good responses. I'll add my bit.

Chickens evolved to molt in the fall when days are getting shorter to replace worn-out feathers. They stop laying and use the nutrition that was going to make eggs to instead grow feathers. We just passed the winter solstice so the days have just stopped getting shorter in the northern hemisphere. Some pullets skip the molt their first fall/winter and continue laying until the following fall, but some do not skip the molt. Some hens and pullets that molt will resume laying whenever they finish the molt, others wait until the days get longer in the spring.

Each chicken is an individual, you can always get exceptions. But the vast majority of mature hens follow this pattern unless you manipulate the lighting so they can't tell the days are getting shorter. Pullets of the production breeds tend to skip the molt their first fall/winter and continue laying while others have more of a tendency to molt their first fall/winter. But each pullet is an individual and can vary wildly. With living animals like chickens it is not absolutely this or absolutely that, anything can happen.

Good luck!