The first thing I would check is to see if your monitor's calibration profile has become corrupted. Lightroom is more sensitive to this than other apps are.
What do you mean by "check the colorspace on the Mac display"?
It should have a display profile on system level (preferably one made with a calibrator), and this is the one Lightroom will use. There is normally no need for any user intervention here, unless you deliberately want to change the profile.
Is this a single display, or a dual display setup? If the latter, there have been reports of Lightroom using the wrong profile - but this is usually a problem on system (not application) level.
Just so we're clear - if you change any display settings, you also need to change to the corresponding display profile, the one that describes that display response. This is done automatically in some calibration software.
But note that this also means you need to relaunch Lightroom. It loads the display profile at startup, and will continue to use the same profile until next launch.