Aww mama, sudden changes like this at that age can be a bit worrying lah, I understand! Could be many things, growth spurt, reflux, wind, or even just a day where baby is extra unsettled, but since she's refusing feeds and crying all day, better to check with your pediatrician or clinic just to rule out anything like tongue tie, infection, or tummy issues, ya? One of my mum friends' baby did something similar and turned out she had a bit of reflux, so don't worry, it's usually something simple once the doc checks. In the meantime, make sure she's still having wet diapers and not running a fever, those are your peace-of-mind checks while you wait to see the doctor. Hang in there, mama!