I looked it up, and I am going to confirm what the people above me said, it sounds like curled toe paralysis caused by riboflavin deficiency. I'm no expert, I just looked it up in a book.
The book, btw, is the Chicken Health Handbook by Gail Damerow, a useful thing that I think every chicken owner should have. It helps you identify diseases, but it does not give any ideas as to how to treat nutritional deficiencies.
I also found this site,
http://www.anyvitamins.com/vitamin-b2-riboflavin-info.htm
It's about riboflavin, also known as B2. Most of this concerns humans, but it does have this useful piece of information at the end as to good sources of riboflavin.
"Organ meats, nuts, cheese, eggs, milk and lean meat are great sources of riboflavin, but is also available in good quantities in green leafy vegetables, fish, legumes, whole grains, and yogurt."
If you are feeding chicks on a commercial ration, I would say, switch off it immediately! It's not giving your chicks what they need.
Always give your chickens treats, regardless of what you feed them! Chickens will generally know what they need to eat to stay healthy. Example: I once accidentally gave my chickens buckwheat grain in their treat mix (buckwheat causes photosensitivity in chickens). They ate around the buckwheat and only the wheat berries and oats, which are all right.
Just make sure nothing you feed your chickens has salt on it. You don't want to give your chooks salt poisoning!
~Skip
