so i made a yeast starter using wlp830 german lager, im very ocd with my cleaning and sanitizing (so i thought), anyway had it on a stir plate 24 hours then put it in the fridge to settle out. it was in the fridge for 3-4 days before i got to brew, needless to say i decanted and pitched and i don't know why but decided to taste a drop of the slurry that what was left in the flask after pitching and it was tart/sour, im surprised it went sour that quick and probably gonna have a sour pilsner as a result lol , will adding hops to the starter wort give it more protection from souring bacteria/organisms or is it just a matter that my sanitation procedure is not as thorough as i think it is and i need to tighten my belt, thank you