I'm new to this forum so bear with me but I need some expertise as I'm new to raising chickens. I have a beautiful road island red that's 9 months old. I noticed this morning while I started my daily routine tr hat this hen was very lethargic and was trembling slightly. There is no sign of injury although her come is starting to turn black. I noticed that she has very watery diarrhea which smells very bad and her craw is very large and tight more so than the others. Shes is not eating or drinking at the moment and is separate from the other 28 chickens. My chickens are kept very clean because I'm a neat freak and there straw bedding is changed every 3 days. They have constant access to fresh food and pellets. I started adding some vitamins to the water as recommended 2 weeks ago to give them a little extra perk as the weather is getting colder. Can anyone offer any advise?