Link devaluation overnight?

Anyone seen a possible link devaluation (rather than a penalty) since yesterday? I've lost about 25% of traffic, nothing major, sure I can recover
Just wondered if anyone else has seen this as I use SER to generate about 80% of my traffic. And it's across 4 of my sites, but not the new ones, always a sign...

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I've been using some of the WP analytics plugins, but none are really a touch on Google Anal