My chickens are about 11 months old. Lost none raising them. In the last, about three weeks, lost one a week. Put them to bed at night in there fairly big, 6x6x12 foot house. I have always locked them in at night. No high roost. No change in food .Plenty of water. I will say, I think it may have been the collection of droppings, maybe caused to much dust with them being locked in. Does have an open roof vent. Since last death. 2 days ago. I cleaned house out. I bought disinfectant but haven't used it yet. I'm now leaving the door open at night. Their yard is very inclosed. I had thought my male duck was killing them at night. Not so. I have put him in his own area since before the last death. Now no deaths but it hasn't been a week yet. Any thoughts? How often do you clean your hen house? Does anyone have thoughts on ducks with chickens?