Penguin hadn�t primarily to do with duplicate content...It was majorly a fight against link spamming/ trading and all other kinds of webspam...If your traffic has plummeted around 24th April, chances are good you were hammered by the Penguin...Make sure you remove all unnatural/ spammy links to your site, there is no overoptimization of on-page elements and most importantly, you have variation in anchor text used.