 SP Dow Jones Indices late Monday announced several component changes to its SP MidCap 400 and SP SmallCap 600 indexes, including refiner and current SP SmallCap 600 constituent PBF Energy Inc. s:PBF replacing Nu Skin Enterprises Inc. NUS, 2.99 in the SP MidCap 400. Multilevel marketing company Nu Skin replaces PBF Energy in the SP SmallCap 600, the index provider said. 