when i start bottoming out it is usually because I haven't eaten enough before the ride or during. I also tend to cramp more easily and charlie horse whenever I end up short on potassium so I am careful to eat a banana before I ride, and possibly a second one during the ride. Around here I tend to go through more water when it is coo and dry, because I know I don't notice the sweat and don't get thirsty. I carry two bottles, one with FRS (my version of electrolytes) and one with plain water. In case I have to refill, I carry extra FRS tubes and start with the FRS bottle.

Sounds to me like a combination of not enough to eat or drink and not enough layering combined with an increased mileage which may or may not have been a big bite to chew.

marni