If I had the domain name I would have better consult you in this regard but at the moment there are lot of maybe’s in my answer.
Here I go!
Adsense click explosion:
There can be multiple good and bad reasons for this:
There is a strong possibility that your competitors have done something stupid that increase your adsense click ratio to be insanely high and on the other hand there is a possibility that some of your powerful readers (with a big fan following on social networks) share some of your stuff that result in more clicks than normal.
One thing is sure that any problem with adsense should not result in ranking drops.
Drop in Rakings:
There are multiple possibilities when it comes to ranking drop:
Check your link profile and see if you find anything suspicious there in-case of yes you probably should look in to your link profile and clean as many links as possible. Also, give another look to your website and see if all SEO factors are available and not really missing anything.
Usually change in theme affect the website rankings negatively, in that case my advice is to plan a content marketing strategy that bring you some quality new links that point back to your website.
If the ranking drop is due to the change in theme, the drop probably will be temporary and will be fixed accordingly.
Hope this helps!