Since you've had them for a year and they weren't chicks, they'll all molt now or soon. It is something all chickens do every year after their first autumn. Some will even molt their first autumn if they hatched early in the year.
You'll have a dearth of eggs for a while. Some people add a couple young birds each year to get through that time.
I add birds year round but still start hoarding eggs in August so I don't have to buy store eggs.
They feel like crap when they are growing a new winter coat. Feathers are 93% protein, They can't grow them and kick out a 6 gram lump of protein every day.
As was said, boosting protein can help. You have a few choices. You can switch all birds to a higher protein grower or All-Flock feed and provide oyster shell in a separate container for any birds still laying.
There are layer feeds like 'feather fixer' with higher protein and slightly lower calcium.
You can also offer some fish, meat or other animal protein a couple times a week. I use canned mackerel because it is a cheap source of essential amino acids.