He is feeling a little tired and starting to go to bed earlier and wake up later. The combination of continued radiation treatments, and lots of outdoor activity (the weather has been glorious) may be a bit too much. He was having some dryness in his throat for a couple of days, but that is gone now. It was probably related to some seafood he had those two days.
He has signed up for a correspondence course, so that should give him something to study for awhile.