Baby Vitamins.

My LO is 4mos old na, pero till now wala talaga syang vitamins na tinitake as in wala. Pure bf pala sya. Ok lg ba yun? Adv kasi ng mother ni LIP and tita nya na Doctor (Hindi pedia) is wag daw, dapat daw mag 6mos sya saka mag vitamins na. Ok po ba yun? Napapaisip ako na baka sguro medyo maliit baby ko, dahil dun. 4mos na sya (LALAKI) and 6 kilos plg sya, height nya last na check namin is 59 cm. Is he within the normal range?