Planet13 - 10:20 pm on Aug 15, 2013 (gmt 0)
Are your sure your site:
- Doesn't have spam on it?
- Doesn't have canonical errors?
- Hasn't been hacked / has malware on it?
Also, were you able to rectify whatever it was that Penguin had punished you for?
It seems unusual that your bing and yahoo traffic would decline as well, unless there is something that is being overlooked...