12 wk old fussy!!

Is this normal??? My 12 week old has become unbelievably fussy lately. No fever or anything. Just crying a lot. She eats every 2 hours 4oz of formula. Doesn’t want anymore. Idk what’s going on or is she just developing?? I feel like I’m losing my mind with all the crying. And my 21 month old is unhappy lately too🥲eeekkkkk