I have a small flock of 8 chickens. One of them is a brown Leghorn about 7 months old. She sounds like she needs to blow her nose. Occasionally she will shake her head and I hear the same sound. It does not sound like it's deep in her chest but more in her head. She is a daily layer and eats well. She is energetic and shows no symptoms of being ill. My other chickens are a white Leghorn and a Brahma and both are regular layers about the same age. I also have 2 red sex links, an Easter egger, a Wyandotte, and a black Australorp that have not started laying yet. I keep them in a run about 8' x 15' and they roost in a coop that is 8' x 4'. I let them out for the last two hours of daylight to free range in my backyard. I have their run and the floor of their coop covered in river sand and clean both daily. I have not used any herbicides or disinfectants. I have had them for about a month. Any advice would be appreciated.