That seems like it could most definitely be the issue. Grain blends that are processed by a commercial manufacturer have everything they need for chickens in them; most of us supplement with treats of bread on occasion, but too much bread is not good for them. Plus, it won't have all the nutrients they need. Most likely, she's lacking in some nutrient. Layer mash isn't that expensive - especially for just a few. If you can, try to scrape together enough cash for a bag. I recall that when I had 6 chickens, a bag of layer mash would last me almost a month, and I feed it free choice. I fear that if you don't get them on something with more nutrients, you will have serious issues soon.
Try to be creative - I know how it can be rough at times with this economy, but look around the house, your yard, your barn....maybe you can find something you could sell for a few bucks. If you live in a state with a bottle/can deposit, look around for empty cans/bottles if you have to. If you really look around, you'd be surprised at what you can find to sell! Good luck with your Bandit!