Whole Wheat Sourdough didn't rise 3rd time
I'm pretty new to bread baking. I've done lots of reading which I find interesting and have baked a few white flour loaves. They turned out fine. I baked the whole wheat sourdough recipe from Laurel's Kitchen yesterday and encountered a problem. This recipe is entirely whole wheat except for the sourdough starter. The first two rises were fine, but the third rise, in the pan, was a flop. It rose maybe 50% in 4 hours! I did bake it and it tasted fine. I'm wondering if the yeast got too hot during the third rise. With all rises I put it in the oven after turning the oven on and off for 30 secs. The 3rd rising period was in the oven for 30 minutes and on a heating pad for the other 3+ hours! I had the pad on low at first and then bumped it up after an hour or so. I had a towel on the pad and a plastic container over the top of the bread.
Her recipe states the 3rd rise will take half as long as the 2nd which would have been about an hour. I would have expected to see some rising within 30 minutes which I barely saw.
What most perpexes me is that if it rose fine the first two times why not the 3rd, unless as I said, maybe I got it too warm.