I agree things just happen sometimes I lost 3 chicks in one day for no reason, so this is what I do when I raise under a broody
1. After I know she's going to set I put her in my broody momma apartment which is a large metal dog kennel with plastic hardware clothes around it and a heat lamp over it and her own food and water. I actually have to feed my silkie in her nest because she will not get off of it.
2. Week 1: After the chicks hatch I replace the layer mash with non medicated chick starter and make sure they all have clean water everyday
3. Week 2: Mom usually starts getting cabin fever so I let her out for a little bit but keep the chicks in the kennel and I start putting some hen scratch in the kennel and mom starts showing them how to scratch around it's really cute to watch
4. Week 3: Mom starts staying out longer and the chicks start wanting to follow so I usually let them out in the coop with me watching them for a little bit before putting them all back in
5. Week 4: Mom has usually had enough and gets to rejoin the flock during the day and that's when i usually put up the chickie fence so they can come out of the kennel and scratch around the coop but no one can bother them but everyone is back in the kennel at night when it's cold
6. Week 5-6: they start to have free reign in the coop and mom shows them where the flock feed and water is
7. Week 7-8 they get to go outside of the coop and mom shows then where the best goodies are
8. Week 8 and on they are full members of the flock and have their own feeder with chick feed but most of the time they eat what mom is eating and scratching around for the goodies i pitch out(apples,oranges,bread,egg and their favorite hen scratch)
It took me a while to finally get a system that works good for me