Just thinking . . . general recommendation for temperature is 90˚F first week, dropping five degrees a week till the brooder is the same as the rest of their world.
So, 90 minus (7 times 5) is 90 minus 35 is 55. I think. Yes, that's the arithmetic. So the brooder temperature can be around 55. They may be a bit too warm. Or he may be. I have some runners who have different temperature tolerances. And the buffs definitely like it cooler than the runners.
And I know they are supposed to know enough to move away from the light when they are too warm, and don't tell him I said this, but some of them don't seem to read the books and do the right thing. Mine never ever have huddled together for warmth. Ever. Even though they were cold and shivering. Just don't do it.
(I need to turn in - please let us know how it's going . . . . )