I got 8 new hens about 2 months ago. One of them has been coughing with rattling breath sounds since I got her. It has not gotten any better or any worse and none of the other chickens have caught whatever it is. Her eggs also have a rough chalky shell and today's egg was super small. I was thinking it might infectious bronchitis, but doesn't that usually runs its course and then clear up? Two months seems to be a long time to have it without getting any better or worse. She acts completely normal otherwise, active, eating and drinking fine, etc. Also, the entire flock was wormed a few weeks ago when one of them had roundworms. Ideas?