Thanks for the pleasure over the years - I started reading about 6 or 7 years ago, and still binge occasionally....
Oh, you said, "The same whiteboard, the same wall, even a couple of the
same markers, if you can believe it. They're even the
same tubes in the fluorescent light fixture overhead."
Change the tubes, Doc - the light output from tubes slowly falls over time, and you don't notice it, but replace ONE tube in a two-tube fitting, and you'll probably see a difference in light output. And it's usually a good idea to replace the starters as well - they age as fast as the tubes do, and a dying starter can get a healthy tube flickering. And modern tubes put out a bit more light for the same AC input, and may be less prone to causing strobe effects on your rotating machines.