Baby chicks do not need to be warm ALL the time.
They like to run around and eat and drink, then go warm up, then run around again.
For warming up, they can do it under a mother hen, or under a heat lamp, or snuggled together in a box, or next to a bottle of hot water, or something like that. With a heat lamp, it's best to have the "warm" place be about 32 to 35 degreees Celsius (90 to 95 degrees Fahrenheit, about the same as human body temperature.)
They need enough light to see during the day. If you have a blanket over their coop, make sure they get enough light during the day.
The first few days are when they need the most heat, and as they get bigger and grow feathers they are fine in cooler temperatures. So if they're already made it to 5 days and seem fine, you might just continue what you are doing.