One of my barred rocks suddenly died today. I noticed late yesterday afternoon she wasn't with the rest of the girls. After looking for several minutes I finally found her tucked between our log pile and water purifier. There was a little fecal matter on the ground and some stuck to her hind feathers. I prodded her to move and some of it fell away. I carefly cut away what remained. She never headed to the coop later that evening, so I carried her there and gave her an appropriate dose of baby aspirin. This morning she came out on her own, but then I found her lying in the shrubs around noon. I put her near the water and gave her a little aspirin water again. Around 2:00 I found her still lying near the water, so I brought her inside to a more comfy area. I checked her again around 4:00 and noticed she had significant discharge on the mat near her head, coming from her mouth or nasal area. I went to check on her again around 6 and she was dead. What could run through her so quickly and are the rest of my girls in danger?