My 19-week old Buff Orpington pullet was full of sass and spunk until yesterday, when she seemed unnaturally quiet. I also noticed some dark runny poo in the coop. Today, when I let the girls out, I saw a bit more dark, runny poo. When I offered cracked corn, plain yogurt and hard-boiled eggs, she came and stood nearby, all puffed up with her tail tucked and didn't eat much of anything, which is extraordinarily unusual. She is drinking. The other two pullets - her sisters - seem normal. I hope someone with more experience than me can provide some guidance. Thank you, Katy