If the LEDs are damaged, none of the DC voltages will be correct.
Re-did the test. I still want to get a more sensitive meter, but I got pretty much the same results. At half-volume, both red and white read 1.2. At full volume its 3.8 - white and 4.2-4.3 - red. So, still about 1 dB difference. It does however seem less noticeable.