Sorry to hear of your rough day, man. It's hard to stay in peak shape for five months. Did the heat and dehydration contribute? In any case, I hope you feel better this week - recovering after 13.6 km isn't easy.
Thanks bro. Possible that the humidity contributed - it is unknown to me.
You've done a lot of training and racing this summer. After WOC its understandable to be a bit burned out and take a break.
You had a very good year because you worked hard. By seeing your form fade when not working so hard (1- 2 hours / week at least that what AP says) is just confirmation that what you are doing is working. Plan your off season and be ready for being sluggish and slow (comparatively of course to your top shape self :) )
Also form is individual. I have friends that need 2 - 3 weeks and they are in top-ish form and more and harder workouts don't give them much additional improvements. I on the other hand respond more or less liner to training at least to whatever level I have pushed in the past.
Find out how you respond long term and short term to training and use it to optimize your trainings and adjust your expectations of your body and form.
TG noted that it was really humid that weekend, and I think we were all suffering more than we realized despite the relatively benign temperatures.
Sucks to feel that way. I suspect it was partly humidity, partly getting your legs woken back up. You were fit enough at the end of August that you can't have lost that much in three weeks. So a hard weekend to shake things up, physiologically, could be just what you need for good performance at NAOC. Keep the faith, believe that you can (or us can), and take some rest to show up on Friday ready to fight.