Hi mama! I think best talaga na mag-check ka muna with your pediatrician kasi depende sa age ng baby at kung bakit slow ang weight gain, sometimes kailangan lang ng proper latch or feeding schedule, hindi necessarily vitamins. One of my mum friends, baby niya naman okay lang after nag-adjust kami ng feeding routine niya, so baka yan muna i-explore with your doc first, yah?