Are there any parents whose children gained weight on mixed feeding? I…

Are there any parents whose children gained weight on mixed feeding? I have a third child who was on mixed feeding, my two older ones were breastfed. We've gained a bit over a month and now we weigh 5250, but we were born at 3520. Has anyone had this experience? Because there wasn't such a thing with scary stories and I don't know if it's normal.