I have indeed upped the heat with a proper IR bulb. Keeping the temp around 90 +/- about 3 degrees. My brooder is on an enclosed sun porch, night time temps have been 60's and lower 70's. I have a good quality digital thermometer in my storage container turned brooder. Initially I had trouble regulating the temp with the 250W IR lamp, temps running too high, I figured out how to adjust the hight of the lamp over the brooder and added a Lutron lamp dimmer to help adjust the temps.
By week 3 they should be between 80-85 . Panting, dehydration and pasty butt are sure signs of excessive heat. I use an infra red lamp on a chain , each week I raise it a little higher and by 5-6 weeks they are outside .