How old are your chicks? Most people recommend not giving anything other than their chick starter for the first two weeks so that they get the complete nutrition they need and learn for sure what their food is. I am still new myself but from what I've read I personally think the best first treats and the reason they are good are-
1. Going outside and pecking in the grass- because this is the most natural thing and whatever they find out there builds their immune systems.
2. Plain yogurt with live, active cultures mixed with their chick starter- the yogurt has protein, calcium and beneficial bacterias, the chick starter is their main food anyway and nutrionally complete
3. Boiled and mashed egg yolk- egg yolk after all was their first food!
This is where I started mine out and so far so good, everyone is healthy and happy.
Also remember chicks need some form of grit to help digest any food other than their chick starter.