I am a new chicken owner and I have 15 chicks that turns 3 weeks old today. Starting yesterday, I heard some teeny little puff sounds that are very quiet but I think they are sneezes. At first I thought it was just one, but most of them (if not all) seem to be doing it now and again today. Also, every once in a while one will make a "yawning" motion by opening its mouth wide and stertching out its neck and closing its eyes. This was a rare occurrence today but just now one Buff Orpington chick laid down to sleep and was doing it over and over again. Otherwise, all seem healthy and happy... they eat and sleep and play and bug each other and they fly around and perch on things and climb on things. Could they be sick or am I being overly paranoid??