Ang bright yellow at slightly watery poop ay pretty normal sa mixed fed babies, lalo na since nag-switch kayo ng formula, ang body ni baby ay nag-adjust pa lang, kaya common yan makita ang changes sa consistency at frequency! Ang sounds sa tyan niya (gas, bubbling) ay totally normal din, especially pag may formula involved, pero if meron siyang signs ng discomfort like excessive crying, bloating, or if ang poop niya ay naging green or may mucus, better check with your pedia para ma-rule out ang possible formula sensitivity or gas issues, better safe than sorry talaga, especially since baguhan pa lang siya sa Nan HA! Hang in there, mama, the poop phase gets less stressful once you know what's normal for your baby.