Thought my sourdough starter was dead, turns out I was just killing it with tap water
After 3 weeks of flat loaves and zero rise I almost tossed the jar, then a baker at the Des Moines farmers market asked if I was using tap water and told me the chlorine was nuking my yeast. Switched to filtered water and it doubled in 4 hours. What's the dumbest thing you did that wrecked your starter?