Gerber soothe formula mucus stool

So my baby (11 weeks) has been on Gerber gentle formula. He does good with it but he's always been gassy. I decided to try Gerber soothe formula to see if that would help him. It's been 3 days and so far he's been fussy. Today he was crying so I used the windi (let's the gas out). A bunch of gas came out but then this blob of green/yellow mucus came out. I know a switch in formula usually need a few days of adjustment but he shouldn't be pooping like that. Has anyone had anything like that happen? He's also been spitting up more. I don't really want to give him any more of that formula.