Shorter daylight hours mean a huge drop in egg production. Hens need about 14 hours of light per day to lay. Some people put a light in there on a timer so they keep laying, and your ladies are going to need extra supplements, both for any chance to keep laying, and to boost their immunity.
While you want to keep the coop warm, insulation can build up humidity, and the buildup of ammonia gas from their poop can damage their lungs. Damp living conditions and huddling together for warmth make it easy for disease to take hold in your flock.