(Please keep in mind, this is my first batch of baby chickens, so do take that into consideration when reading my thoughts on the topic. Also, looking forward to everyone else's posts on this subject. Thanks!)
I have 27 chicks that are currently 8 weeks old. For the last 4 weeks they go through a 50 lb bag of chick starter every other week. They have a feeder available during daylight hours that is always full. They do get a treat of bread or veggies about every other day or so and they have access to my garden for about an hour near the end of each day. I know they are suplementing their diet with insects as there is now not a single grashhopper or tomato worm in there, and it used to be well infested (no chemical defenses in there - it's survival of the strongest). Don't know if this is normal, but that's what's happening here and the birds are growing like weeds.