Oo talaga, mabagal ang pag-adjust ng babies sa new formula, lalo na kung galing sa ibang brand, kaya normal yan for 2 days pa lang pero I'd really suggest checking with your pedia to make sure baby's hydrated okay at walang other concerns. A few of us tried switching formulas din and iba-iba ang reaction ng babies, pero kung sigurado ka na Nestogen lang ang bagay, maybe the tummy needs more time to get used to it, or kaya mag-try ng different feeding schedule or bottle position, pero yun, best to confirm with your doctor na okay lang talaga baby, especially pag first time nagswitch.