Molting--how long & how to help

I have 8 hens--2 Blue Stars & 3 Bovans hatched about a year ago, and 3 Bovans hatched about 6 months ago. Except for some sudden, extremely cold weather right before Thanksgiving, they've been inside their raised coop, inside a barn, overnights. No heat but I do keep a thermometer inside. So far, it's never been lower than 20 F.

It looks like at least one of the older Bovans has started to molt. I wasn't sure at first as this is our first time wintering our flock. She also seems to have an occasional sniffle that hasn't gotten better or worse over the past 3 weeks. She doesn't act sick & is eating and behaving normally. I haven't seen any feathers from the Blue Stars--just red from the older Bovans.

Right now, they're still getting about a quart of laying mash (we got 4 eggs yesterday & 3 today) and pretty much all the scratch corn they want. They have access to a fenced yard when we let them out of the coop late mornings. If there's snow on the ground, they stay in the barn. I can tell from the colors of the eggs who is laying and who is not, and it looks like none of the older Bovans are right now.

1) Should I worry about the sniffle? It's occasional, not constant.

2) What can I do to help the process along?

Many thanks from a worried mama.