Make sure they cannot get into their drinking water source when temps get down below freezing That could cause frost bite if allowed to sit in it over night. And sounds to me like you might need more ventilation in your house if humidity is at 73%. What kind of window do you have can it open from the top? that way humidity can escape but wind isn't blowing right over your babies. Or if you have a walk in basement you could do like @Amiga and keep them in there over winter.