It is strange that a mixed flock of hens in their first winter would go so long without laying eggs.
Have you tried letting them out to forage a little?
have you tried adding supplemental light in the coop? They say that laying hens should have 14 hours of light per day.
At first I thought it was their second winter, and then I saw that it was their first winter, so I changed my response.
The egg laying of chickens is generally affected by the length of the day. It can also be affected if it is extremely cold, but I know that is not a problem in your neck of...