Not sure where exactly. The restaurant/farm owner never got back to me, but if you did happen to contact her through the Backwoods Crossing website and find out where in GA she gets her chickens, let me know!
Brahmas are awesome. Going back to the title of your thread, they do need a good quality feed to thrive. They're heavy, slow growers--not an economic "high feed conversion" breed.
I don't love commercial feed, and but after having chickens, I'm so grateful we don't have to source our own grain and minerals, mix, and store it all just right. Nutrition is so important. Chickens hide illnesses, so if they aren't getting the right nutrients, you probably won't know until it's too late, and/or they've stopped laying and are covered in parasites.
Seems like almost no 2 chicken people feed the same way. We've settled on an 18% protein "chick starter" for chickens of all ages, with no less than 0.4% methionine. Depending on whether it's laying or molting season, we mix in a couple other types of feed with higher calcium and protein.