Starter up to 8 weeks
Grower Crumbles or pellets from 8 weeks until you get your first egg
Layer from first egg on.
I use starter/grower until I get my first egg then I switch the girls to layer. I personally use crumbles. I tried a small bag of pellets but they didn't seem to eat it to well, so I switched back to crumbles, but I started them on crumbles. I smashed up the pellets and mixed it with their crumbles. If I have any starter/grower left when they start laying, I mix it with the layer until it's gone. I haven't had any problems with my big girls laying. I personally use the medicated starter/grower. I don't start to give young chicks treats, etc. until they are a month. When I give them treats I give them grit in a separate bowl as free choice.
Chickens do not have teeth. Their food goes, as is, into the crop, where it is slowly funneled into a very small " stomach" for some digestive additives--then to the Gizzard, where it is 'chewed', that is, ground into material that can be digested as it moves into the intestines and so on. The Gizzard is best able to break down whole grains and other chunky bits that they eat when full of grit. Longest lasting grit is Granite, that lasts well. All other rock and stone is so much softer, that it wears down fast and that is why granite grit is best choice, works really well for best utilization of feeds. My baby chicks are given free choice and they choose it with pleasure, baby grit is fine Granite, as soon as they are given anything besides Starter Crumbles. If you can't find any chick grit, then just smash up some regular granite or pigeon grit. Their tiny gizzards are at optimum function at an early age.