Sick chicken-not walking??

One of my hens has had trouble walking! I noticed this about a week ago when moving them all to their new home, it is like she's drunk, she's falling over and can hardly walk and her tail is down. She did have a swelling on her front but this has now gone..I have been told it could be barley poisoning as I feed them crushed corn grown here on the farm but can anyone help me here? She doesn't seem to be getting any better! Sally