Everything that's in a chick grower/starter is exactly what they need until they hit laying age, then they need an all flock feed or something higher in protein with calcium on the side. Depending on the breeds you have, layer feed will not have enough calcium for healthy development of eggs.
Scratch grain almost seems like a good way to get your birds fat and unhealthy to get them sick so you buy more birds and repeat the cycle. Scratch grain is like candy for chickens and builds up lots of excess fat in the bird's body.
When I slaughtered one of my birds, when I used to follow a friend's advice on feeding methods, they were VERY fatty/obese and it was probably the reason why she stopped laying and got so unhealthy. I mixed scratch into their regular food, just like you, and it was just so bad for her and her health.