I have a 7 month old Buff that have been rather lethargic for the past two days. Her waddle and face seems dull and pale and her balance seems off. She did lay yesterday prior to this onset and she also picked at scratch this evening. None of our other 8 hens seems affected and we have not added any new hens in about a month.her stool was a frothyish yellow last night. Thanks for and advice!