Never in 3 years it happened so it’s freaking me out. Impressions are fine. Just CTR is down.
If you made any changes to your site, just revert it. If you didn’t then the best you can do is just wait and let time solve the problem. My ctr is also down but not too down. If Adsense is experiementing with your Ads then you may see a fall in ctr, same with what happened when experimenting with Link ad units.
Haven’t made any changes. So I guess I just have to wait.