Just want you to be careful; sounds like you may be 'overtraining'. If you don't mix it up a bit on your rides, it's just plain necessary to have days where you take it easy.

Drop it a couple of gears, and just spin. It's good training too, as you can work on your pedal stroke. The same thing happened to me 2 years ago, and it was because I was riding in the same gears, all the time. I wouldn't shift down, simply because "well, I always ride in this gear, what's wrong with me?". What was wrong was that my legs needed a rest. I listened to some sound advice from some other cyclist I know, and the chief recommendation was after 2 or 3 day hard sessions, have at least 1 'spin' day.

It can be hard to adjust to dropping the gears, but keep your cadence up, and try to keep your stroke technically correct. Try that for a couple of days (cleaning the chain and tire pressure are also good suggestions by the crew), and see if this gets you where you want to go.

Also, I always, and I mean always, take two lumps of whey protein before bed. I can ride like a nut 50-60 miles to work (sometimes I get up early if it's nice, mid-week or so), ride home (20 miles), and be almost as good the next day. If I don't, I'm very sore, and more important, stiff as a board the following morning.

I doubt it's what you're eating (unless it's fried chicken and donuts, that might be a problem); I don't know about you, but if I'm hungry, I know about it pretty quick on a ride.