Sayang, baby weight yang naik-turun macam tu normal dalam few weeks first, tapi since you're worried about jaundice turun and baby's weight dropping, please check with your pediatrician or clinic ASAP, derang kena assess baby properly.
Milk changes won't be the main reason untuk weight loss at this stage; it's usually about latch or feeding frequency. Your doctor boleh guide you properly on feeding and confirm baby's health okay!