I have never seen a drop like this in audience and I'm not doing anything differently here on my blog. Yet, the traffic suddenly swan-dived to about 200 per day, the lowest since I started blogging in 2010. Presumably, a minor adjustment / correction wouldn't result in such a radical and immediate shift like this -- what should I be on the lookout for? Is Google penalizing me specifically? Was there a major update in mid-January?