I recently baked a loaf that was 100% bread flour, 78% hydration, and a 100% hydration whole wheat starter. It bulk fermented for 4.5 hours at room temperature. I did 3 stretch and folds every 15 minutes then 3 more stretch and folds every 30 minutes and finished bulk fermenting for 1.5 hours. The oven spring is not too bad but the crumb is uneven and a bit gummy.
How do I fix this?