No, you are not crazy (well, possibly not), and yes, you probably have seen a change in your search ranking performance over the last week.
Google has now confirmed that a new “broad core algorithm update” has been released. We usually see these updates once or twice a year and usually without warning.
Here is the official statement from Google on Twitter:
Each day, Google usually releases one or more changes designed to improve our results. Some are focused around specific improvements. Some are broad changes. Last week, we released a broad core algorithm update. We do these routinely several times per year.
As with any update, some sites may note drops or gains. There’s nothing wrong with pages that may now perform less well. Instead, it’s that changes to our systems are benefiting pages that were previously under-rewarded.
There’s no “fix” for pages that may perform less well other than to remain focused on building great content. Over time, it may be that your content may rise relative to other pages.
Now would be a good time to audit your SEO efforts and re-look at your strategy.