I have a adult flock of 4 hens and a rooster and a flock of 6, 5 mth old babies( Americauna/ Russian orloff X) that I incubated myself from my adults hens and rooster. Up until a month ago, the babies had been living in the garage and then I put them out with the adults, but seperated. They could see one another and shared half the coop and half the pen. On Monday I found a home for the baby rooster, so on Tuesday, I took the barrier down and allowed both flocks to come together, but at night I've still seperated them. The babies pretty much stay in their group and the adults in theirs, though they swap thru out the day of sides of the pen. There are the times when a baby will get near the adults and be ran off. But over all it's gone smoother then I thought. On Friday I let the entire flock out of the pen to free range in the yard. The babies pretty much stayed near the door and forged around the coop house. I was counting babies and noticed one missing. I found the one with half her body under the house. The adults go there to bathe, so I assumed she was doing the same. I noticed later on she was breathing with her beak open, I made sure there was plenty of water in both water containers( one near the adults and one closer to babies) and there was indeed plenty of water, so I thought it was because it was a warm day(70's here in Washington state) and didn't think nothing more about it. At dusk I went to make sure everyone was in , so I could lock them up. The babies were in and hanging out on their perch as normal, all hudled together, but I did notice the one baby was still breathing with her mouth open. I made note of it and went in for the night. Saturday my husband let the flocks out and as I was rushing to leave I made sure they had food and water and was gone until dark , so my husband locked them up for the night. This morning, Sunday, I let the flocks out, fed them and rushed to church. When I got home, I went to let both flocks free range in the yard and I nocticed only 5 babies. My stomach felt sick as I looked, hoping she was just hanging inside the pen, but I immediately realized it was the one baby hen that had been breathing with her beak open. When I didn't see her in the pen, I went to the coop dreading the worse, and there she was, right below the perch, stiff and probably had died in the night Saturday night, which makes me sick as her owner to know I didn't discover her until the next day and that her sisters had to step on her to roost that night and the morning after. I noticed some clear liquid from her beak, but nothing else was wrong with her. I just want to make sure it's nothing contagious that could attack the rest of the babies/adults. I'm new to having chickens and don't know if this is normal or what to look to with the others and what to do if I do notice others breathing funny. Do I try to treat them all , but what am I treating? I love my chickens and try very hard to give them a good life. They are fed organic food with suppliments of fresh fruits and veggies. I have hand held the babies from the day they hatched, which was good Friday. Loosing one of them is horrible!! Any thoughts/ideas/answers are greatly appreciated.