Switching formula

Hi my twins just turned a month old yesterday and I switched them from enfamil newborn to enfamil infant yesterday as well. After their second feeding (4oz each) on the infant they cried for about 2 hours straight and seemed to be in pain I’ve never seen them cry like that then I gave them (2oz each) and they cried for a little bit until I rocked them to sleep in their rock n plays. Today they seem to be a little better. Just wonder if that’s normal when switching formulas. I didn’t think there was that much difference between the 2 formulas.