Eh, muntah sikit after formula mmg boleh happen especially kalau baby baru adjust ke formula, tapi since dia dulu ok dengan susu, kena monitor carefully lah. A few of my mum friends pun ada baby yang muntah when they switched, tapi kena tengok if it's just a little bit atau banyak, and if baby still active dan happy or lethargic. Better check with your doctor first to make sure dia tak ada intolerance or lain-lain, sebab switching formula lagi banyak times sometimes boleh confuse baby's stomach.