Wow, this is interesting. Are you able to share the "cheap" brands? I'd like to stay away from them.
In various emergencies when I couldn't get to the farm store or had to buy something else because the store didn't have any of the all flock, I've gotten the cheap layer from Wal-Mart, from Tractor Supply, and from Southern States.
The common factor is that it was cheap, 16% layer. I don't think brand matters significantly because the same thing happened with any brand of this type of feed.