70 isn't nearly warm enough for 2 week olds. It may not kill them cause they will huddle together but from everything I have read they need to be kept at 95 the first week dropping it 5 degrees each week. So they should be 85 to 90 right now. This is what I have done with mine and had success. I keep a light on in one corner of the brooder so if they get cold they can go there to get warm, then move away during the heat of the day.