Isn't hay really bad for winter and/or possibly all of the time? Their crop can be impacted by eating it, it doesn't absorb moisture very well and generally molds instead of drying out?
It locks in moisture, which is the exact opposite of what you are looking to do. Sure it treats the dry'ed comb, but unless it just a single cold snap and is moving back to warmer weather, it does more damage than it does cure.
If they are still on chick feed, I wouldn't offer them OS, depending on their age, their kidneys are still developing and you don't want additional calcium until they lay their first egg.