Not lethargic, seems to be normal in every way ... though it is midnight so he's a little sleepy as it's past both our bedtimes.
Because I am slightly disabled a dog walker takes him for an evening walk and she does not know if he found something on the ground sometime in the last week or so that he's eaten; certainly could have done so. Otherwise no major changes in diet (though I use different brands of wet/dry food from time to time).
I will get my bathroom scales to weigh him, but his weight has not changed noticeably -- very healthy.
Actually -- the gums DO LOOK QUITE PALE -- that's definitely out of the ordinary!