You can really overheat ducks way easier than chicks.
Keeping a heatlamp on them till feathered would be way too much for them.
Unless they are in a super large brooder or coop where they can get far away from the lamp...
Like chickencanoe already said it will be dependent on the temperature of the room they are in.
If they are in the house and its 70 or more they will most likely be fine without heat at this age.
I brooded mine outside and by 3 weeks they slept by the 70 degree corner but not too close.
I had...