I would start working on weaning them off heat...Raising the lamp or moving it further away, or swapping to a lower wattage bulb, will help with that.
A simple first step: move the heat lamp to one corner of the brooder, so the other corner is a bit cooler. Then yes, I agree to swap it for a lower-wattage bulb or move it outside the brooder so it shines in but doesn't put in as much heat.
Even when they first hatch, chicks do not need 90 degrees everywhere. They need one spot that warm, but it is good for them to have cooler areas as well. Then they can adjust themselves to varied temperatures by moving around. They start to enjoy the lower temperatures from a very young age, as long as they have a place to warm up when they feel chilly.In the room it’s around 70, In the brooder it’s 90