Are you sure they are warm enough? If the room is 65, you need a pretty good temperature increase to get to 90-95. Have you ruled out a draft? Even if a portion of the brooder is registering a 90-95 degree temp on the thermometer, a draft from a 65 degree basement can take the felt temperature (wind chill) down quite a bit. Since the brooder is in a basement, are you sure the temp stays at 65 at night? It could be dropping significantly lower at night. If you don't adjust the light for that temperature dip, they may be getting too cold. Are they able to get to the warm area? If you have feeders or other items blocking the way, very young chicks may not be able to figure out how to get where they want to go. Usually that is a concern for only the first few days.
That's all I can think of that hasn't already been addressed. If you have ruled out any causes over which you have control, you may want to contact Ideal about replacement chicks.
Good luck and let us know how things end up.
UGCM