The first thing is your set up is all wrong your chicken coop should be bigger and off the ground and the floor should be wood with air holes for fresh air on the sides of .box size should be 4by4 feet .outside pen ten ft.by five ft. I know this will help
Even though there is fresh shavings, just a few days later I pick up the food feeder to refill it and there is white fuzz mold on the shavings underneath the feeder
My intuition is telling me this is the wrong design. The litter should be in an enclosed weather proof area. Because it rains a lot and it just gets all wet and nasty in there. I feel as if this whole thing needs to be lifted off the ground. I suspect the ground underneath the coop is now super nasty and is breeding bad insects. Because even though its new fresh shavings, there are still a few tiny gnats and other super tiny bugs crawling around.
This is my first time having chickens. When I started this a few months ago in November 2018 I had 3 chickens. About 2 weeks ago, a few days after I cleaned the coop with new shavings, Penelope was wheezing/sneezing. I went to work and bought VetRX. I come home, only 6 hours later, and she was near death. Her comb turned purple. I poured a few drops of the medicine in her mouth and this seemed to make it worse. And then right there in front of me she started flopping around and died on her back with her feet in the air

It was a horrible experience and made me feel like a terrible human being.
Another thing I noticed was two of them had dark black oil spots near their comb on their head, which then progressed to a small bald spot. I'm pretty sure its from them scratching their itch. After I changed the litter, their bald spots grew back (new feathers with a lighter color).
I suspect they are not eating as much when the feeder is inside the coop, so I put their feeder outside the coop and they made a mess with food on the ground around the feeder. A few days later there is white fuzz mold on the ground where the food fell.[/QUOTE]