She was fine SUN afternoon and even laid. Yesterday afternoon yellow runny poop and lethargic. This morning dead. Other 5 hens showing no signs. Had always had issues with runny stool and dirty vent with the hen that died but she always laid good and seemed fine. I know some of you will probably throw out Blackhead but I don't know. I'm hoping it was just something internal with her. Besides I've read that blackhead is carried by chickens but chickens don't get it, turkeys do. Anyway, y'all think I should Medicate the others with something? If so, what? Only thing I have ever used is D-earth. All the the hens are roughly a year old.