4 days ago I noticed one of my 14 chickens was sitting down a lot. The next night she wasn't roosting so I put her up there and she was having trouble keeping her balance. Yesterday and today she's been acting drunk or like the videos of the cows with "mad cow" disease. She can no longer stand or keep herself upright. If I pick her up the legs will move and work but if I put her down she's falling over or leaning to the side. Doesn't have any other symptoms and continues to eat, drink and poop. The poop does look a little runny today so I will worm her but any suggestions would help. I know some might say cull but I would like to give it a chance. Please advise. Thanks in advance