Keep this handy with you. Baby poop will change colour as you BM/FM. Newborn will be black, then after you give BM will be yellowish/mustard and FM will be greenish/light green/pale green. You might want to change the milk brand again. Due to the FM taken, baby's digestion change and react therefore after the process, poop colour change/smell. It can be like a metallic smell like iron/sulfur. My first LO started with Similac 0 to 13 months and my second LO was Dulac but now change to Soy Based for the time being due to recent diarrheoa issue (side effect of her vaccine)
Only started giving formula after 6 mths. And it was BM/FM thereafter with other foods. Din hv any issue with their poop.
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