Kelsey:
I looked at your blog and spotted a few trouble spots. Without addressing them the results are unpredictable. Injuries, muscle fatigue, etc would not be a surprise.
http://kelseystraining.fastrunningblog.com/blog-week-03-29-2009.html"Hooray for not being too busy to cook dinner!"
I take it that being able to cook dinner is an unusual occasion. What happens on the nights when you are too busy to cook dinner?
Your good dinner contained white flour and refined sugars, so I think it is safe to assume bad dinners contain that as well. Some bodies are stronger than others and could handle that with almost no effect on the recovery and overall body health. Others are not that strong. I know mine is not. For me, white flour without refined sugars had a cost of almost 6 minutes in the marathon. I do not know about what it would have been with the refined sugars.
You do not run 6 days a week for fear of being injured, but you did 4x1200 on March 31. Then a tempo run two days later. In your current state you should direct all of your running capability to running as often as you can and as many miles as possible. Refer to
http://asksasha.com/Running/Top-10-Training-Mistakes.html