Here is the short of it,
I have had chickens for 7-8 years. Mostly just 3-5 at a time that free ranged around the house and hedge row. Last April I decided to get a little more sophisticated and I built a 16 x 16 coop that has nesting boxes and roosting polls. I also built a 1/4 acre run that is on the backside of my coop that my chickens have access to all the time. I started with 18 chickens and over the last month I have lost one a week for a total of 4 that have died. I treat my chickens with Wazine twice a year. I also have shavings in the bottom of the coop. I cleaned my coop out 2 weeks ago and treated it for mites and bugs.
I also have a separate pen up off the ground away from my larger chickens that I raise chicks in until they are larger enough to go into the large coop. I keep about 25 chicks in it. I have lost roughly 8-10 chicks over the last 3-4 weeks as well. I spend time with my chicks daily and have not noticed any signs of illness until yesterday. I inspected the dead chick and this is what I found. Please let me know your thoughts.