This is horribly sad and I'm so sorry this is happening to your family - but thank you for keeping us all posted so we can learn from the situation. Wishing Mouse a speedy recovery. :hugs
I was reading this thread hoping for a happy ending. I’m so very sorry for your loss. Others may have suggestion on cause and what to do to ensure it doesn’t impact the rest of your flock. Since it started suddenly and with a leg issue, I’m wondering if it’s possible that it was a snake bite or...