If you were using that coop as a brooder with no hen, you would be fine with ONE heat lamp heating ONE small space to 95 degrees at chick-height, with feed and water near the outer edge of the lit/heated circle, and the rest of the space as cool as it naturally gets.
Given that the chicks do have a mother hen, I would certainly go down to one heat lamp, and adjust it to provide a single warm area near the food & water, instead of trying to heat the whole space.
The more they have access to cool space, the more quickly they will grow feathers and be able to deal with cold. And as long as they can warm up whenever they want (under the hen, or under a heat lamp), they will not be stressed by having cold areas available to play in.