I’ve made this and have had trouble with getting stains (even pre-treated) out of my kids clothes.
A fantastic pretreater is Fels-Naptha straight up. Either rub the bar on the stain, or put the bar in a jar of water and let it melt into a gel. Either way, I have had no trouble. It even takes the stain and smell out of clothes that have baby spit-up on them. Plus, Fels-Naptha is $1.12 at Walmart. Much cheeper than fancy pretreaters!