Yes, I would continue to use the heat lamp/light at night. Watch your chicks. If they are all huddled under the heat source then they are too cold. If they are all as far away as they can get from the heat source then they are too hot. There should be some under and some away from and some meandering around - then they are ok.
My chicks never have liked the 95 degrees that is called for and I have raised a few different groups. However, I always start them out with this temp on one side or directly in the middle of the brooder so they can move away from it.
Even now, I have a brooder set up and the chicks are staying far away from the heat light where it is 80 degrees most of the time and going for the cooler side of the box where the thermometer says 74 degrees.
I don't know if they sleep where it is warmer or not but even in the mornings they are huddled closer to the cooler part. I have their food and water in the middle so they know where the warmer side is and often venture over there but never stay. And it is getting in the low 60's here at night.
All I can say is I got me some cool chicks!