The slow feathering could indicate that you have a cockerel. But, some birds just feather slower. My Columbian Wyandotte was the slowest at feathering of all my chicks, but in the end, she became just as fluffy as the others. Wyandottes, in particular, seem to be slow at feathering in some cases. As long as your chick acts normal, "it" is probably fine and will grow up eventually.