I have a 3 year old RIR that began walking backwards a couple of weeks ago. She is at the end of a heavy molt during which she experienced an impacted crop, weight loss, increased thirst, and loose droppings. She has these same symptoms every fall when she molts, along with an exaggerated gait occasionally throughout the day, where she lifts her feet really high as she walks. This year after taking several exaggerated steps forward, she will put her head down and walk backwards for 8-10 steps. Most of the time she walks and runs about normally, but several times each day, mostly in the morning, she walks in this bizarre manner. I switched my flock from layer to grower food several weeks ago when they started molting, and add poultry Nutri-Drench to their water a couple of times a week while they are molting. She is re-growing her feathers nicely and putting on weight and is really looking much better, but the backward walking is scary to watch. I don't know about a vitamin deficiency. Generally I think my girls eat well, but I have no other ideas what might cause this. It's comforting, though, to know I'm not the only one to see this bizarre behavior. I wish I had some advice for you!