I started testing the LEDs on the KY11 front panel tonight. The process was simple: apply power to the panel, and ground each pin one by one.
There was only one dead LED, but several others were barely visible so I decided to replace them too. Unfortunately, the new LEDs are noticeably brighter than the old LEDs (though drawing the same current), so I ended up pulling and replacing ALL of them.
Normally I’d hate to do a wholesale replacement like that, but in this case I think it’ll be worth it.