For family reasons (child to look after) I can't keep a close eye on my SEO and SERPs. But from top 10 rankings in January for a dozen keywords I'm now not in top 80 results -- save one keyword for which I'm ~18-20.
Not a sitewide penalty: some of my internal pages are still ranking top 3 or so.
In GWT, late March I received warning of a rise in server errors:
17 Server Errors/575 soft 404s/17 Not Founds/Access Denied 1/Others 4
I've also got 2 very old sitemaps (from two different ex-SEO firms) & I'm guessing about 75% of the links on there no longer exist.
Q: Could all this be behind my calamitous SERPS drop? Or should I be devoting my -- limited -- time to improving my links?