I set this aside for a couple hours as I had to get on a call and do some grinding for work... figured I'd clear out some time to get my other monitor out of the closet and give it a go
upon waking up my monitor from sleep mode, all of the colors are bright and vivid again. what the actual fark.
I had already rebooted a couple of times and re-installed my GPU drivers before my first post, so I don't know why the monitor sleeping and waking up would change anything, but it did.
I went back into my LG On Screen Display Calibration, and confirmed that the settings are unchanged, Picture Mode is set to VIVID at 84 brightness.
I did a tiny bit of experimenting and noticed that after changing the Picture Mode to SRGB, the brightness was set to 14 and the picture was quite dim, similar to what I'd noted earlier. I changed it to 84 and it looks pretty normal.
I'm pretty sure I previously had the setting on Vivid, and I hadn't changed any of the settings when I noticed the dim effect earlier, so I don't know if Picture Mode + Brightness was the culprit or not... it doesn't seem likely.
Anyway, I think that things are back to normal, but it's hard to tell... I think the colors still look a bit de-saturated.
I fuckin hate troubleshooting.