Brown streaks in vomit

Hi everyone!

I just woke my LO up from a nap to feed before bed. I had him on the changing table he was fine and happy smiling away! Then all of a sudden a spout of vomit came shooting out of him ! It had this brown streaks in it. It smelt bitter like acid reflux smell. I did just start him on kendamil a few days ago, would that be the cause of his throw up? He seems fine still happy and didn’t cry at all when it happened. You think it could just be the formula? We were on enfamil before the switch. He just seemed more gassy on that that’s why I switched him. He also has breast milk morning and night (I stopped producing enough to feed all day and he doesn’t breastfeed anymore) has this happened to anyone?