I have 19 total birds that vary in age from 20 weeks to 2 years old. I bought many of them at different times and from different people. I have noticed since it has started to get colder (about 40 F at night) that a bunch of me hens seem congested and especially at night and in the early mornings seem to try to blow air and shake their heads as they get up and start moving from the perch. I have never noticed any discharge. Is this congestion normal? Or is it something i should be worried about. I don't know if any of the birds were ever vaccinated.