I had a momma hatch 1 chick a few weeks ago. We kept them separate for a few days then it seems she really wanted to stretch her legs. So we let her (and a baby) run in the coop while the other birds were kept outside. Within a week we let them all mix because it seemed momma was taking care of baby. Then we found baby dead after another day or so. Now, another momma might hatch 1 chick. We will keep them separate a lot longer, but I don't know how long is appropriate. Any suggestions?