Baby spitting up a lot, could it be new formula?

So my baby is 3 weeks old today, and from day 3 I have been giving him half breastmilk and half formula. The formula the hospitals gave us was Similac Pro Advance step 1 so we’ve been sticking to that, but my parents got us 4 cases of Enfamil A+ powder formula so I switched to that 2 days ago since we ran out of our Similac and figured we’d use up the free formula cause formula can be expensive.

Since then my baby has been spitting up a lot more, and a lot in terms of volume. 2x today he spit up enough on the bassinet that it was all on the back of his head and got his hair all dirty I had to wash it off, and he spit up a bunch on my shoulder too and that I had to change shirts.

I mixed it right, and it’s still only half and half breastmilk and formula but I can’t think it’s anything else. Did anyone else have problems with this formula? He’s not allergic or gassy, and burps fine. Eats big (he’s already 10.5lbs) was born big and has been a big eater since day 1. Eating about 4oz bottles each feed.

Any advice?