jakebohall - 7:57 pm on May 21, 2013 (gmt 0)
I would leave things be and see what happens. If you notice the site is continuing to drop, then you can reach out to see if there has been some manual penalty.
Considering the drops seem pretty minimal, and some of them kept you on the first page, I would assume it is something algorithmic. If you see things continuing to fall, I would pull a copy of my backlink profile and see if all your incoming links match up to what you would expect.. basically checking to see if someone is hammering you with spam links.