Hi Nutty! Sounds like you're doing a great job with your chicks. Cracked corn and scratch is like candy to a chicken, so throwing a handful in for your flock to peck at about once a day is just fine.
Veggies and fruits are a good treat. Lots of people feed their chickens dinner leftovers, and I don't think that's a good idea because chickens can develop fatty liver disease, and that shortens their life.
If your chicks have been in their run for a week or so, you might be surprised to find they'll go into their coop when it starts getting dark, even without the bribe.
Not sure what your climate is like, but I'm in Ohio, and cracked corn or scratch is a real good bedtime snack in the winter for chickens, because it's harder to digest, so it brings their body temps up, and helps keep them warm.
I'd stick to the starter/grower feed until they are about 20 weeks, then I switch to the layer feed.
That's my story and I'm stickin' to it!
Sharon