I posted a little about this yesterday but my baby has been formula fed since she was born and at the hospital she got similac pro advanced and thats what she took until wic gave me gerber gentle. While she was on similac she never spit up unless i didnt burp her right and she pooped fine. And then when she got gerber gentle she started pooping like an amry green color and a mash potatoe consistancy. And last night she threw up while i burped her. And after that she was fuzzy during her feedings and she had so much gas and she would take the bottle but she wouldnt drink. We switched her back to the similac and thankfully she started eating but when i burped her a little spit up came back. Please tell me what it could be. I read that a little spit up when theyre burped is fine and im not worried about that im just curious why she reacted so much better to similac the second time.

I have an appointment with her pediatrician ln wednesday and i plan on telling her but i just want to know why the gerber formula barely made her start throwing up after being on it for two weeks.