Back on the sprout diet, with a caveat: make sure the grains are in good condition and not mouldy!
Here goes with the recipe:
10% lucerne chaff soaked in molasses water
5% sunflower, pea and lupins.
Ritual: every 4 days tip 4 days' worth of wheat and corn into a large bucket, and fill the bucket to the top with water. After 24 hours strain the grain and hang them in a bag to drain completely. Over 4 days, feed either the soaked or sprouting or fully sprouted grains with other additives as above (chaff, molasses, sunflower etc).
Sprouting doesn't add vitamins or amino acids but it does 'unlock' vitamins that are there already and that might otherwise pass through the bird's digestive system.
The above diet will need a few added extras if you want it to be a permanent thing. Firstly free range or good fresh green pick (mainly for vitamin A, which ensures good immunity). Secondly, sunlight (for vitamin D). Thirdly, calcium (e.g. shell grit) for layers. Fourthly, a few of the necessary amino acids are best supplied by meat. Ideally this would be insects from free range, but at certain times of the year (or in a small yard) insects can be in short supply. A handful of meat meal, fish meal or similar can go a long way when the other inclusions are sprouts.
You can add seaweed meal and other supplements like dolomite for minerals, but be careful about quantities, particularly with seaweed (which can be extremely high in iodine). If you do add minerals, it's a good idea to provide them in a small hopper so birds can take the amount they need.
One last thing: salt. Chickens can't handle too much, but they do need a little of it, so the odd family meal scraps or leftover bread can fill the requirement.