My daughter just made 5 months on April 26th. She has been formula fed similac advance since she was three days old. She’s never had a problem with reflux. I could count on one hand the times she’s spit up.

A few days ago she started spitting up. I recently ran out of similac and bought up&up brand, but the spitting up started BEFORE I switched. And it’s still happening. It isn’t after every single bottle, but it’s every day and more than once a day. And it’s not the entire bottle coming back up, just normal amount of spit up.

Why is this happening? Can babies develop reflux at this age? Should I change her to gentle?