I have an 8 month old Saipan pullet, normally weighing about 8 or 9 lbs. Lately I've noticed she's been having very runny and dark poo, and she won't lay anymore. I know laying slows down in winter, but her sister at the same age has been laying at least one egg every other day since mid-December. This morning it was around 30 degrees outside, yet there my sick baby was, laying down in the cold pen, while the other chickens were in the coop. I didn't know what to do so I just brought her some warm water and some new food. Which brings me to say that we just changed their food, because they hated another kind that we had bought. They wouldn't eat it at all. So they only free-ranged for their food for about 3 days before we ended up buying some new food. I know that dogs and cats get sick sometimes when you change their food, could this be something like that? She's been sick-looking for about a week, and I've noticed she's lost some weight. Any help is greatly appreciated.