Pekin bantam has hatched out 11 of 13 eggs. 6 black and 5 white. We put the heating lamp in with her, in two big boxes, with room for all to move about. Day 5 have noticed that she is pecking at the black chicks especially when feeding, passing all the white chicks to get to the black chicks. Any particular reason for this?? Black chicks running away from her. Hen even trying to get under what lamp to get at the black chicks. This is strange. Is this normal?