Did you just have a growth spurt? We did around this time. For a few days after the growth spurt, he reduced his intake. But he went back to normal after this. We then went straight into a regression.
For about a week and a half/ she seems to have gone back to normal with her feeds except her morning one she is still a bit fussy - having around 34-38oz a day
I think fussing or crying or becoming difficult with feeds is a part of the four month regression / developmental changes. My baby is EBF but has become much fussier on the boob/ cries and it is much harder to get him to have a full feed in one go. So frustrating! Just as they get more efficient at feeding so you’re not constantly breast feeding this happens