My 2.5month old baby is 4.3kgs( birth weight- 2.9kg, reduced to 2.7kg). My doctor said baby is under weight hence asked me give formula-feed along with breast milk (90ml in the morning and in the evening). I am even expressing the milk and giving it to her if she falls asleep when feeding. Doctor has provided iron drops as well(It's been 2days I am using those). Today she had green poop, what may be the reason?