Could my 4 week old baby be lactose intolerant?

My daughter is almost 4 weeks old, when she was born she was put on enfamil formula. It made her spit up lot so she was switched to similac sensitive for fussiness and gas. This worked well, we started the ready to feed then when to the powder, and it both worked fine. I am on WIC so we tried to use the good start sensitive concentrate formula. She's been on it for the past two days, and has been spitting up almost an ounce after every feeding. She seems to have a lot more gas, and it takes her a while to settle down. She usually drinks 3-4 ounces every three hours or so. Should I go back to the similac, since it seems to be the good start?