Because the difference was so dramatic, I checked to see if I had done anything on Sept 5th and found that I had installed a couple of Wordpress Plugins. The one I thought could have possibly impacted the bounce rate was SEO Booster Lite. But I had no way of knowing. Now, I am completely perplexed because, to the best of my knowledge, I haven't done anything different with the content but the bounce rate has gone back.
My site gets approx 1250 visits per day. It's called the LA Progressive.