My chickens all seem happy, and healthy. They run around without gasping. The one year olds all have scraggly feathers this year. But sometimes when they struggle they gasp. One of them will yawn over and over just standing there. Today one was pecked and afterwards she stood still with her head up gasping, her comb got really dark but not purple. Sometimes if some of them eat too fast it's like they have trouble swallowing? They move their heads and necks like they are trying to get food down? What is wrong? Over a year ago I brought a new chicken into the flock that shook her head and yawned once in a while but it went away so I thought it was better. Help.