the only thing is I started using Google Adwords to promote from 9th Sep.
I had been sending Bing traffic to a page with one Adsense bottom banner on it for years, with no problems. Suddenly, on August 31, the epc and ctr on that page tanked. Then the rpm for the entire site tanked by about 25%. So I took Adsense off that page, and the rpm came back up almost immediately. Now the rpm is higer than it was when I was running Bing to the site. I imagine that if that happened with Bing traffic, then they are doing the same to Adsense sites with Adwords traffic.