I have lost 5 chickens in the last 1.5 with no signs of sickness until that day when I either found them dead or they wont get up and then later that day they passed. I have now treated them for upper respiratory infection and coccydosis by medicine in water 2xs now. Yesterday Another one of my chickens wouldnt get up, so this morning I brought her in and have been watching her. I thought maybe it was too hot. I dont know if I need to vaccinate them again or if something else is going on. The chicken just wont stand up, seems alert but keep the feathers spread out and will drink if you make it. My chickens are about 3.5 months old. Any thoughts on what is going on??