Hi Michele, if you're weighing your ingredients, using our flour, and are able to keep a constant temperature of 72°F, then the variable that is likely slowing your dough down is the activity level of your sourdough starter. You might want to try using sourdough starter that has been fed a bit more recently and see if that improves the 12-hour rise. Using older discard is likely to cause the dough to be slower to rise, and it sounds like extending the rise didn't prove helpful to you. I think, ideally, I would look for the dough to double during that 12-hour period in order to ensure that it will continue to ferment and rise appropriately in the fridge. If your home happened to be a lot cooler, extending the rise time might not cause issues, but I suspect in your case this caused the dough to over-ferment a bit. As far as refrigerator temperature goes, the FDA recommends keeping the temperature at 40°F or less, so you might want to turn it down a notch. 

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