I just came home from work to find my 3 year old barred rock hen lethargic in the side yard. Her comb was pale and a bit scratched up, her eyes barely open with a small amount of blood at the top corner. She did not come for food when I put it out and only perked up mildly when I went to see her. I brought her inside to give her a check up. She was limp with labored breathing. Her crop felt fine and I could not detect an egg that was bound (she just finished a hard molt and I don't think she was close to production yet). I offered her water but she refused it. She just lay head on the floor breathing hard. She suddenly squawked and thrashed on the floor. She did this several more times (seizures?) curling up her neck with her eyes dilated and her tongue protruding slightly from her beak. She stopped breathing and went still. I do not know what caused this but have three other hens in my flock who seem fine for now. Please help me figure out what killed my hen.