TIL my sourdough starter went from smelling like nail polish remover to smelling like yogurt in 3 weeks, but is the yogurt smell actually what I want? | Baking Fails And Wins - Discusd
The yogurt smell is exactly what you want, means the good bacteria took over. Mine did the same thing around week 3 and now it makes awesome bread. If it smells like nail polish again just feed it more often.