I would say they are still to young and should have the heat. Depends on your temps as to when you will be able to get rid of the heat light. Usually 6-8 weeks I think. Depending on how cold it is, mine will still get a heat light for a while when they move to the coop. Our nights are still cold here and my 4wk old chicks are in the brooder in the garage.
Hello...the answer to your question is 6-8 weeks...you can gradually lift the lamp a little higher each week, as they will grow quickly, require less heat, and will start to knock their little heads on the lamp if it's too low, but besides this, they need the warmth of the lamp to keep warm as they are not snuggled under a mama hen!
Before you take away the heat the chicks need to be fully feathered out with more mature feathering. Some chicks are feathered at about 8 weeks while others can take as long as 12 weeks. Don't be in too much of a hurry to take away the heat. As this is still very early spring and temps drop at night the chicks can get chilled. Very often when a chick gets chilled it gets sick and this can be fatal. You can weaned them slowly from the heat lamp by turning it off on warm days and raising it a little each couple of nights. Last year I had to keep heat on my spring chicks until mid June. The night air was just too cold for them with out the heat lamp - and I live in central Virginia.