Worrying trends

I am continuing to see a general drop-off in Adsense clicks and earnings in the last month of so, I would estimate that earnings could have as much as halved recently. I do not track earnings closely enough to be absolutely sure at this stage whether I am losing out in terms od clicks, traffic or CPC - I know I should be on top of this, but I tend to concentrate on working at the coal face when I have time, rather than analysing the results.
My main worry is that this is where I want to concentrate in the future, ie. passive earnings through contextual advertising and affiliates. What this tells me is that I need to track trends a lot better than I do if I want this to work for me in the future. In other news, I am on the very cusp of moving to a new hosting service which will allow me to move domains onto a single hosting package - for now, I am happy to maintain blogs on the 'blogger' platform, but I do also plan to experiment with Wordpress too for some other sites.