It depends on if they are free range or not. If they are, then they don't need any at all right now. If they are getting decent laying hen feed, you actually don't need to give them any scratch at all. Think of scratch as dog treats. Your dog does fine with kibble, and the treat is extra. I...
It's probably just fat. She could have a tumor or something. Just monitor her.... Not sure what to do. If you are giving her a lot of scratch, especially corn, it's probably fat. Fat birds don't lay eggs very well.