2-year-old Americauna, she'd been panting and making an unusual chirpy squawking noise for the last three or four days, but still seemed to be eating, drinking, pooping, and laying normally. At first I attributed it to the heat. I put some ACV in the water yesterday. Two hours ago, I went to let them out and she wouldn't leave the coop. Twenty minutes ago I went to check on her and she was dead. I have two other hens who seem just fine--can I let them back into the coop, or should I empty it and clean it out thoroughly first? Also, I have three pullets and a cockerel arriving tomorrow. What timing. I planned to keep them in a separate run in a dog kennel until they all got used to each other, but now I'm not sure what I should do with them. What could it have been, and could it be contagious? I'm really sad about losing my girl, but I'm concerned about the others. I would be very grateful for some advice.