the chicks are still very young they probably don't have a lead chick yet,mine were still in the house at that age when we built their coop I kept them in that for about 2 weeks before actually letting them out in the run, then I needed to lift them into the coop when it was getting dark, they would huddle in a corner of the run, it takes time, remember they are babies all their instincts haven't kicked in yet they're at the age that its more important feel the heat from the others, your the mother you need to keep putting them in until they are old enough to realise it for themselves.