The brooder should be 95-100 the first week, then drop it 5 degrees per week thereafter. That is just guidance. It is best to watch the chicks and how they respond to the heat. If they are panting, decrease heat (lift light higher away from them). If they are cuddled under the light or piling on top of each other, they are cold (lower the light closer to them). When they look happy, you have it right.
By the time they get to about 6 weeks old, they can tolerate about 70 degrees safely and should have most of their plumage to regulate their own temperature.
Jody