concerned and confused

by robin
(conowingo md)

My chickens are 2 yrs old and I have never had a problem until about 6 months ago they started losing feathers I thought they were molting but the feathers have not come back so I used a dusting powder I purchased from a feed store that the store clerk advised for possible mites. I dusted the chickens and the hen house and the entire area, this did not help. Now one by one they are bleeding from the but and dying within 3 days once that starts. I dont know what to do. I feed them chicken pellets cracked corn and noodles every day. We let them out once a week to run around the fenced in yard. I dont know what else to try. Please help.