That's why the rule with Adsense is: if it ain't broke, don't fix it :o)
Search engine traffic is easier to manage with changes like domain names as long as you do everything right technically
Adsense is a different beast and you never know how it will react to a major move like that. Well now you know, and hopefully you can get back to the same level as you did before
And since your revenue has already fallen, why not use this time to change things around. Doing the same thing as you did before did not work, so shake it up a bit -- change where you're putting the ads, change the ad formats, change the color, anything -- and see if that will work.