I just made four loaves of sourdough white bread. It rose like crazy in the bulk rise and pretty well in the bannetons. I transferred it to the oven - a 1" stone on the top shelf and baking sheets on the bottom and an iron frying pan in the bottom to which I added water when I put the bread in. I baked it at 500 for 20 minutes and 425 for another 30. After the 50 minutes, the crumb was chewy and sour though pretty dense, and the crust, well, there wasn't any. It was just smooth and white. What did I do wrong?