I have heard a lot about feeding BOSS (black oil sunflower seed). Is is the same thing you buy for cardinals? How often do you give it to your birds and at what age is it safe to give. Is it more of a treat?
Boss is good to up the protein levels in their diet, but corn is higher carbs and is like candy to them. Too much is bad for the diet, as it would be for a toddler. I have read in many places including BYC that treats should be rare, no more than once a week. I subscribe to this as it is easier than calculating the percentages of nutrients they are taking in. You should give no more than the birds can finish in 10-15 minutes. You can use the shelled or whole varieties as they love both. That is what I do with the treats, but others have different takes on the info.
Read up on nutrition for your babies as there is a great deal of stuff here in the learning center.
The idea of a treat being only once a week, well, if it is a "empty calorie" type treat, then I would agree with that. Pieces of bread, corn (which is mostly carbs), and other things like that -- yeah, those things should be limited, IMHO.
But other treats are healthy for the chooks: yogurt, greens, BOSS, raw milk (but not storebought, pasturized stuff), scrabled or chopped boiled eggs, garden vegetables, mealworms.... these treats are healthy, nutritious treats, and it doesn't hurt to give the birds some of these alot more than just once a week.
I get my BOSS at the feed store and it is mixed into their food so they get it everyday. I miss it 1:6 1 part BOSS and 6 parts layer crumbles along with other great goodies...here is a video of their mix minus their red winter wheat and rolled barley which is in it now. They scarf it down but eat less of this than their layer food alone plus their eggs are better and their laying is great.