Our almost three year old Silver-laced Wyandotte hen is seeming quite sickly. One of a mixed flock of 5 hens that free range in our fenced city yard. This is our first flock and we have had no illnesses since they were purchased as chicks. They eat laying mash from the local feed mill, supplemented with veggies from us and anything they can find and dig up in the yard. The other 4 appear fine, nobody has been laying the past 6 weeks due to lack of light, it only recently got cold enough for the heat lamp in the coop/run (they have done this every late fall). She has always been the biggest and strongest hen, but hasn't been perching the past week or so, has a bit of trouble walking long distances (strength seems to fade) and has lost weight. She has been eating and drinking, although today seems less excited to move around and feed, more content to just sit. There is plenty of feces stuck to her feathers around the vent, not sure if it is actual diarrhea or just because she is sitting on the ground most of the time. Any ideas?