Sourness

Sour notes - I am fermenting two batches of Dude's Lakewalk right now, but I think I have a problem with one batch. One is 21 days old, and the other is 14 days old. The older one is noticeably more sour on the finish than the other, which I consider near perfect. The batch in question had mash temp problems (overshot strike), and I used Biscuit instead of toasting 2 row pale as the recipe calls for. Any thoughts as to what might be making this beer more tart? My sanitation is pretty solid I think. Aeration and dry-hop are the weakest links in the process, I guess. This beer normally has a citrusy quality to it (Amarillo, Simcoe), whith a hint of tartness, but I am worried out this one.

Any words of wisdom appreciated.