I've experienced something this month with AdSense that seems counterintuitive, but is happening nonetheless. My main site is on track this month (April) to have probably 1,000 fewer visits and 5,000 or so fewer ad impressions than the previous month, yet I'm also on track to make about $70 to $80 more than I did last month. I've seen my first $10 days ever this month -- four of them, in fact -- and generally my earnings have been their best ever, even with less traffic than the previous month. Any ideas why? Interested to hear your perspectives.
Did you change your ad positioning or anything else? Otherwise, maybe it's just normal business fluctuations.
Track your ads with a tracking script. There are 2 or 3 good ones for Adsense. See what people are actually clicking on. Advertisers change bids all the time, new advertisers come on board. Google decides your site has more "value" do to linking factors so you can make more. With a tracking script you'll know which colors work, which ads are being clicked on, etc. Then get rid of the ads that are not performing at all. Google trewards not the volume of ads but the quality and performance of those that are clicked. You don't need to have 3 ad sets on a page to make money. I do very well on some sites with only 1 ad unit block. Sometimes people need fewer options not more.