I've been feeding all my chickens fermented Scratch and Peck brand corn and soy free feed since the oldest (3.5 months old) we're two weeks old. I also have a batch of 6 week olds and a batch of 1 week old chicks.
I ferment in a half gallon mason jar with a lose lid (I'm looking for a piece of window screen to replace the seal piece for better airflow). My girls and boys are in a cycle where they get one day fermented, two days fermented, three days fermented and then back to one, except during those times when they suddenly eat infinitely more, then it's a one and two day cycle until they drop back down. I ferment just with water, and sometimes add herbs, usually a couple of times a week. I also keep set Scratch and Peck in the feeder just in case but that's usually only for emergency back-up as they prefer it less.
For water, I put Braggs ACC with mother in their inside waterer (plastic), and occasional crushed garlic. In the outside waterer (metal) I add fresh herbs when we have them on hand or ready to harvest (basil, oregano, cilantro, rosemary, etc).
All of my chickens are extremely happy and healthy and I attribute this to all the good stuff they're fed, and getting to forage all day.