First time chicken owner. My 24 week old PR hen just died in my lap. This morning everyone was fine. 11 girls and a roo. 10 now. Just now i went to give water and table scraps she came runnng. Everyone went for the fresh cold water as its been a hot day. She stayed at the door. I noticed she was panting....not unusaual on hot days however she was now layimg and one foot wouldnt uncurl. I sit with my girls every morning with my coffee and several times through out the day. This was a sudden onset. I took her out, she doesnt like to be held but didnt resist. On the porch i tried to give her water.within 5 min she couldnt hold her head up. Her gasping became worse. Her poop was normal. One foot curled and comb was faded. Within 10 min of me getting her out she was dead in my lap. No injuries, no lice or body mites. Vent was clean. I did notice her legs were a little rough but only just read about leg mites. Dont have a refrence as to what they look like yet (ill google after i post). Evryone else is fine......my roo is calling for her. What could have caused this to suddenly happen? This is my first loss. Im worried about the others. Any advice appreciated. Ive reseached marek and the vaccine its self scares me. I try to keep them 100% organic.