Formula milk

Hi, my baby is currently 5 months old and recently we started feeding her fm, first night we fed her NTUC house brand because my cousins’ kids are all drink it n they recommended however my girl seem to be allergy to it, red patches started to grow on her body and she can’t stop scratching herself. Second night we tried to feed her nan but she’s still rejecting it but this time round only her mouth area grew red patches. Today I added one scoop to my bm and she drank 100ml only. Her usual intake is about 180-190. #pleasehelp #advicepls