Babies getting squished..

I had my broody Silkie hatch out a batch of silkie chicks. This is her second brood. I didn't loose a single chick from that first brood..This time 4 hatched out, 1 didn't make it out of the egg..

I let her roam around the coop and run like last time.. but I found 1 of the chicks smooshed flat last week.. I thought it had gotten crushed by a big chicken.. walked on perhaps.. so I put in a divider to keep mamma and her 2 remaining chicks seperate from the group. It's a small space but not tiny.. food and water-er.. Today I go out and another baby is crushed dead.. What is going on?? Do I remove the remaining chick and put it under a lamp and raise it that way.. how traumatized with both mamma and baby be? Why is she crushing them???

 

SO.. should I just leave the last chick and hope for the best? I cannot see it doing well if I move it alone.. to a brooder..