3 month old not eating as much as before!!

Ye
My 3 month old baby girl is formula fed and used to eat 20 or more ounces a day of formula. This whole past week I have struggled to get her to eat 14-18 ounces a day! She is as happy as before and having 1-2 dirty diapers and 6+ wet diapers. She has started sucking on her hands a lot. For the past 3-4 days she has put herself on a sort of routine: she is usually asleep for the night by 10-11pm and wakes up at around 5am. This is all the changes I have seen in her, but could have nothing to do with it. IDK. I need help and answers. Anyone have a similar experience or know what could be going on with my baby girl?