If you can get grower switch to grower and if not feed starter until they are close to laying age. Some feed it until they see an egg. I've yet to see grower here. I'm lucky if they have anything besides medicated starter and layer.
Do not mix anything with their feed. Mixing things into their feed can cause problems or at minimum make them dump all the feed out on the ground trying to sort through it then it gets pooped on, mixed in the shavings, and wasted. Anything they can have unlimited should be fed in a seperate container or things like scratch which are a treat should be fed in limited amounts daily. I wouldn't bother giving scratch to young chickens. It's mostly empty calories that they don't need. They just like it. I don't even use scratch or corn. I give mine black oil sunflower seeds in winter. More calories, fat, and useful nutrition.
