Did you plant them when the weather was still very cold (below freezing)? If so then they will be fine and you should just leave them alone. They know what they are doing and they should be fine. I don't remove the tops of my containers until the plants are getting a good size and it is fairly warm on a consistent basis. Of course my containers are in dappled shade in the morning and full shade as of about noon, so no chance of them getting too hot and frying.
Don't bring anything in....just take a deep breath and leave them alone :)

Just wanted to add that if you are really concerned then through an old sheet over them or an old blanket or something. that should keep them protected but remember to remove it first thing in the morning.