May 17, 2014, was the release of the Google Panda 4.0 update.
June 13, 2014, was the date of the Google MetaFilter 2 update (increased traffic to forum sites) and June 12, 2014, was the Google Payday Loan 3.0 update which targeted spammy pages with spammy keyword phrases, spammy page titles and queries.
Google's mobile-friendly algorithm (launched April 21st) completed its roll-out on May 1st, but it can take up to ten days for search results to reflect these changes globally when all affected sites are re-indexed.
My traffic is about what it usually is this time of year for a Friday and Saturday. On Sundays and Mondays, my traffic goes up.
Traffic yesterday to HP was lower than December 25th. In fact, visits haven't been this low since August 23, 2013.
Traffic went down 20% for U.S. views and 18% for global views from the day before. But, that is just one-day's traffic so we can't say that is a trend just yet. According to Quantcast, HP is still the 67th most visited site in the U.S. and #36 globally, so it still compares well to other sites.
In my opinion, the HubPro and EC programs have done nothing to improve traffic site-wide to HP or even to individual Hubs collectively in the programs. Cleaning up the low-quality Hubs still on the site would help, as well as giving greater exposure for highly-trafficked Hubs on Related Hubs, HOTD, Topic pages, etc. Also, as I've mentioned before (to deaf ears), what would help the site gain traction is improvement of content on all Topic pages to make them true landing pages and running PPC ads for them. That would also help in positive branding for HP.
Since HP staff has shifted the emphasis away from traffic, maybe what we are seeing now is the result of that decision.