Sourdough Starter problems, diagnosed

Start with feeding history and temperature. A neglected starter can become sluggish after it uses up its food, while a healthy starter in a cold kitchen can simply take much longer to double. King Arthur notes that a healthy starter at 75°F or above often doubles in about 6 to 8 hours, while temperatures below 68°F can slow fermentation substantially. A brand-new starter can also show an early rise and then go quiet for days before becoming reliably active.