I had three Silkies all sitting on eggs, but only three hatched. Those three chicks are now about a week old. All three hens are kind of caring for them communally, nesting together between two bales of hay. I also have half a dozen three-week-old Marans in the brooder. What is likely to happen if I slip the Marans chicks under the Silkies tonight? Will hens accept chicks that old? Will the older chicks peck the younger?