For those of you interested in the post race debriefing here it is:

That result is exactly what you should expect. While your body gets used to running a lot, you're going to get increasingly slower....for now. When you hit a 40+ mile week, then we'll descend over three weeks back to about 20/25 and start speed. You'll be amazed at how that goes when you have a couple of hundred miles under your belt. Rome wasn't built in a day...:-)

You're doing just right. Most important now is not to overtrain, pay
attention to your body. Mileage is not worth illness/injury.

So there you have it. Straight from the horse's mouth. All's well. The funny thing is that now I'm more motivated than ever to hit a 40 mile week so I can start going back down to my "normal" mileage.