similac spit up formula

Baby was on enfamil newborn formula. She wasn't gaining weight like she should and was spitting up all the time. Doctor switched her to similac spit up formula. She's not really spitting up now but seems like she's pooping less and the texture of her poop has changed. Also, it seems like she doesn't want to eat as much. Is anyone else on this formula or has been in the past that may have noticed something similar with their baby???