I've had a website for almost two months and traffic had been rising overall but today I've seen the traffic has dropped massively at about 1AM UK time:

http://imgur.com/7HHnN

Search impressions: http://imgur.com/1JUO8 (The final date in the graph is the 8th Dec)

It's a coupon website but I've been strictly following Google's guidelines on affiliate sites including being wary of keyword stuffing and the like.

Anyone know why this has would have happened and what I can do?