Figured it out! (see post below)
I have a Canon DSLR with a 28-135mm lens. I was just today taking close-up photos (of my jewelry I sell) when the trouble started. All was fine, I was using manual focus, set it on the nearest focus setting, which allows me to get close enough to my jewelry to take good close-up photos. But between one photo and the next, suddenly I can't focus that close, I have to move way out for the item to be in focus on the nearest setting (which is useless for what I'm doing). Unless I bumped something mysterious, I didn't change anything. (I was using it on M-manual program) When I switch it to auto focus, it also cannot focus as close as it did previously. I'm wondering if this is possibly a broken focusing mechanism inside the lens? And if so, can it be repaired (and is it worth it)? Unfortunately it looks like the nearest camera repair shop is over an hour away, so I'd have to send it off somewhere (where?). I bought the camera and lens lightly used over a year ago, and am not aware of any warranty that would cover it.
This is my "good" camera I use for all my photos (that I don't take with my phone), so I need to figure out what's wrong. Anyone have a clue?