Where did you get the chicks—a breeder, a feed store, or a hatchery. More than likely, they do not have lice or mites at this age, unless you bought them from a breeder with poor conditions. Look their skin over well for any moving bugs. Do not put anything on them unless you confirm lice or mites. If they came from a hatchery or feed store, I would doubt they have any parasites. Chicks do shake their heads, scratch, and have a lot of dander, and that is normal.