Whining chickens?

Ok community, I hope that you can answer some questions that I have.

My chicks are between 7 and 8 weeks old, mostly feathered....so I figured that it would be warm enough last night for them so I switched the heat lamp out for a night light in the coop. Also, I decided that they had learned where the food and water in the run were located (so I took out the food and waterer that I had inside the coop) and left the pop door open for them.

Night drew near and I was in my kitchen and heard the chicks (almost in a panic manner) chirping loudly! I initially thought a critter must be tormenting them. I went out into the run and did a quick inspection and 6 of the birds were huddled in a corner of the run (by the coop ramp) whining and 4 were in the coop ( 2 on roost and 2 whining). I scanned the coop real well and then again the run....NO CRITTER PRESENT!

So, there I was trying to figure out what they were complaining about. I went through the check list: food and water (check), night light on (check), no critter invading the coop (check), and seeing that I had taken out the heat lamp I thought they might be cold, but it was 64 degrees out still. SO what the heck were they so bothered I asked myself? With no obvious answer, I closed up the run doors (we have doors that close over the hardware cloth) to put them asleep as they were making such a fuss, I was worried a neighbor might actually hear them.

They did quiet down by about half the volume, but still were complaining. I went out again into the run. All chicks had moved into the coop (2 were roosting and the rest were huddled together in the opposite corner of the night light (under where the heat lamp would have been).

So my questions are plenty. Does anyone have an opinion on what they were complaining about? Was it the temp? Too many changes at once? Or was it the oncoming storm?

BTW: They are all quiet and acting normal so far today.

Thanks!