Sundial,

If it's as hot in your neck of the wood as it is in mine, then the heat alone may explain your lagging energy. No matter what I eat or drink these days, I just get to a point where I want to be done, off my bike and out of the heat. I am so ready for fall right now.

I can ride for about two hours in cooler temps without food. The hotter it gets, however, the more I need to eat early and often. See if upping your food intake a bit helps. Certainly, finding some shade for a bit of a rest couldn't hurt either.