Iyay, normal lang yan sa formula babies, lalo na sa 4 months! One of my mum friends said the same thing, every feed equals poop, hehe, kaya nauubos ang diapers nang mabilis talaga. As long as hindi yellow-green ang kulay at hindi watery or mucusy (signs ng allergy or infection), okay lang yan, pero best i-check pa din with your doc sa next visit para peace of mind mo, specially kung nag-switch kayo ng formula recently.