How old are the hens? January is one of the coldest and darkest months- it is quite likely they aren't treading or even going to think about laying until the end of Feb. If the hens were hatched early last year, they should have laid through the winter- if hatched late last year it is unlikely they will start laying until end of Feb/ Mar (depends where you are).
I have a breeding pen of bantamns of which none are laying, and I have another pen of laying hens, of which 1 is laying an egg about every 4-5 days. But all my hens are now 2 years or older, and their laying is never as good.
Beth