Well, my silkies have been great moms so far. So I don't think it is that. The brooder is closed but has plenty of ventilation and the heat lamp is on one side and they have plenty of room to get away from it and usually don't sleep under it. We have had a couple of really cool nights too. I have been letting mama and babies out into the run while the other chickens are free ranging. I have to go in and make sure all the babies go back to the brooder and there is usually a couple I have to put in there. Mom can't count and leaves them out there. So I went out last night and it was just this one that was still out and it had started to cool off a bit and it is damp from the rain we have had. It felt a bit chilled but I figured if I put it under mom, it would be fine. So I put it in the brooder. But maybe mom did not let it under her or for some reason it was just already sick and that is why it did not make it. I don't know. I will never again give a broody that many babies. 13 is too many for a silkie for sure. But she took them on her own. Anyway, lesson learned.
Thanks for your suggestions though and your support.
Marie