Ahhh mama, ini normal je la, baby 4 bulan sometimes boleh jadi picky dengan susu baru, especially kalau suddenly tukar brand! A few of my mum friends pun kena sama, anak mereka macam main-main je lepas few days. Try la mix sikit the old formula dengan Dutch Baby untuk transition gradual, bukan sudden change, banyak kali baby akan terima lebih senang kalau rasa dia sama sikit. Also check whether baby demam, ada teething signs, atau perut upset je, sebab sometimes picky drinking is actually a sign something's off. Kalau after a few days still refusing or ada signs lain, better check dengan doc ya, sebab takut ada reflux or sensitivity issue yang baru keluar, better safe than sorry! You're doing great first-time mama, jangan stress too much