Thanks for the ideas. I hope you're right, Chasm, that it is just being tired and not a symptom of overtraining, because I want to train a lot so that the century is enjoyable.

I have to say that I was really exhausted Sunday evening, less "Boy, I'm beat, what a good workout" and more "What is wrong with me?" But maybe that's what tired feels like at 59.

I'll try making the easy rides easier (and longer) and the hard rides harder (and shorter).