About 7 weeks ago, I came out to the coop to find one of my Barred Rocks setting ruffled up on the coop floor. She was very lethargic and had runny, yellow droppings. I brought her in, gave her probiotics, oregano tea, acv & electrolytes. We kept her warm etc. She would eat if food was placed directly in front of her. She sat ruffled up for 4 days with no improvement. Her breathing was heavy. Finally we culled her because it seemed she was suffering and there was zero improvement. This was heartbreaking for us. Then, yesterday I came out to feed, and again found another Barred Rock with a poopy bum and not eating. She was moving around, and by evening was feeding again. This AM she came out with the others and was eating, and then I found her dead about two hours later. I'm extremely concerned this is some type of bacteria or other issue that will continue to spread to my flock. Can anyone give any advice on what this could possibly be?? We've never lost an animal before this, and I'm beside myself to eliminate it before it takes any more of our ladies. We feed an all organic feed with table scraps + supplement with oyster shells. They have free range of the farm. We keep the coop clean with straw for bedding. There are occasionally mice in the coop. They share the farm with horses, goats, dogs, cats, ducks and a pot bellied pig. Please help me to understand what is going on and how I might fix it.