I would try limiting all the additional foods for a little while and mainly feed the layer pellets. Just see how it goes for a few weeks.
It's not that any of the foods you are feeding are bad, they just aren't balanced or complete on their own or in the combination you're feeding them. If you're only feeding a little bit of them, that may not be your problem. If the combination of all of them is adding up to a fair amount of calories, it could be.
The rice bran is a lower protein level than their layer feed and also isn't a complete protein. Grains, including corn, don't have all the amino acids in them that a chicken needs, like animal proteins do. They need to be combined with legumes, to be more useful. Even then, methionine is still usually low.
If it's not diet or lighting, then I don't know what it is. You've already added lighting. Maybe if you go with mainly layer, plus continue the new lighting, you'll see some different results in a few weeks. I know you're trying really hard to give them everything they need. I can only imagine how frustrating it is for you, to still be waiting for egg production to improve. Hang in there.