Robert_Charlton - 6:16 am on Mar 9, 2013 (gmt 0)
I did change all the anchor text on the site from "product Review" to "My Experience With Product A" and so forth.
This brings up another thought, and that's the question of whether you were making changes in response to a ranking change that Google had made previously. If so, take a look also at this discussion...
Google's Rank Modifying Patent for Spam Detection
Here, ranking changes you might see would be in response to changes you make... and would most likely not correlate, eg, with Panda change dates.