Dark, from one who's been through some similar as what you're seeing, a couple of pieces of advice.
1./ Aces is right, move down to lower stakes. To lose that much in 8400 hands, you have to be playing $10 maybe? Move down to $5 or maybe even $2 if you're at $5.
2./ Get out of 6 max, and least for the time being. That game is quite a bit more aggressive and may not be the place for you right now.
For display purposes, try setting up your graph in bbs instead of $$.
Below you will see my graph of the first 26 K hands I played while using PT4. While not as steep as yours, still looks quite similar, doesn't it? You will come out of it. The downswing could be natural, could be because you're playing over your head a little. Like Aces said, step back to lower stakes or take a break and think about it.
For comparative sake, here's the graph since the one above.
[image: http://i.imgur.com/KDvdkjC.png] (http://[IMG]http://i.imgur.com/KDvdkjC.png[/IMG])
Forgot to mention 8400 hands is hardly a decent sample size to look at your overall play and make decisions. It's been said by many before me and much better than I, prove you can win at lowest stakes for something like 50 K or more hands first.