Yes, remove the baby bird and put them in a brooder (or critter carrier with a heat pad under half, lined with a good few inches of aspen/course pine shavings).
I would even take over the feeding just to take all the strain off the hen. Just be sure to prep formula as per package instructions. At 6 wekks old, you can introduce some steamed warm veggies, veggie mash, millet spray after formula feedings.
Did you vet the parents before breeding to be sure they didn´t have any diseases/illnesses that could be passed on to the young?
It´s important to keep the little one warm until their feathers grow back, hopefully they will. One the feathers are back, they will be able to regulate their body temp like an adult bird.
If the parents lay more eggs, remove them, boil, allow to cool and put them back. Parents need to have a break, alying back to back is not good for anyone.
Do you know why the other chicks passed away?
I´ll tag
@finchly and
@Mockinbirdiva in case I missed something..