7.5wk baby drinking less milk

FTM here. This has been happening for a week and a half. 2 days ago my LO was feeding at 120ml per feed. And a week ago only on one of the day my baby was feeding as usual too. Then the following day after those good days feed, she will only drink 30-50ml per feed every 3-4hrs instead of her usual 90-120ml. And she has been sleeping a lot more too. I dont think she is losing weight. She is currently at 5kg. Ive checked her temperature every 2hrs and no fever. I also dont think she has thrush or any illness as she is still the same self. She will constantly fidget and move her hands to her mouth to swipe the bottle away every time as well. I swapped formula yesterday thinking she doesnt want her old formula anymore but the issue still persists. I have also changed her teats from size 1 to 2 and different bottles as well but still the same. Why the sudden change? Any mummies experienced this as well?