I did the math some time back and the feed recipe I came up with was way more expensive than even the organic non-soy non-corn non-canola feed i get for $30 for a 50 # bag.
I too love to make my own yogurt, mayo, laundry detergent, cosmetics etc., fodder and FF for the chickens, have made dog food and so forth. I put the project aside. I love the ingredients in my organic feed.
yes you would need the Fertrell mix. You could consider fish and crab meal and some kelp as well as castor oil. Calcium would need to be added as well to a layer mix.
I was pleased as punch to find my feed as it is produced about 200 miles from me. It is called Big Sky Organic Feed and fortunately my local feed store carries it.
Birds from hatchery stock are typically smaller and may even lay later, I have found. Mine are hatchery stock. I don't think it had to do with the feed. They just weigh less than average I was concerned at one point but since they are in excellent health I have put that worry aside.