When to change formula please help ladies !

If you noticed babythrowing up and on a formula where he didn’t do that on the past formula is that an indication to change it he also has reflux ..is it’s just the reflux getting worse or is it the formula that’s causing it although he had reflux from the previous formula he wasn’t throwing up on it he just had a hard time eating it because of the gas for this one doesn’t give him as much gas but is making him throw up (to throw up looks like spit up just a lot of it a lot!)