This is an awesome story! We have had success in feeding our injured or too thin girls strips of bologna for the extra protien. Don't know if this is a reccomended practice out there or not but may be something to consider, though it sounds like you have a really good program now! Has the dog...
I think all of the above advice sounds really good. Once you start this treatment, we have found that strips of bologna work really good for regaining weight. I am not sure if this would be a reccomended practice but it has worked for us.
We have had similar problems with ours. If you only have a few hens I don't think it is pecking. I would be on the lookout for mites though. This is what has happened to ours in the past. Start giving them anti-mite dustings and see if it helps. Not guaranteeing that this is the problem but...