My basement/floor is pretty cool. I’ve tried moving the lamp higher but then they shiver. I keep a close eye on whether or not they are acting hot or cold. You can’t see it in the picture, but the lamp is suspended from the ceiling and is hanging a good 6 inches above the brooder at the moment.They look pretty well feathered. They most likely do not need the heat lamp. At the very least, you should move it up quite a bit.
You're going to have a beautiful flock.