“People who claim the feed is the problem - GET THE FEED ANALYZED.”
As if there are companies are all over the place that are sophiscated enough to do that.
A better way, much cheaper, and is what people are doing, is to switch feed and see if there is any difference. There is, so, that is why they attribute the difference to the feed.
But there are companies that do it.
The place I get eggs from has not experiences problems (thus far) feeding DuMor, but that is a data point of 1.