Dead LEDs

I made a light a year ago with 10 Samsung strips SI - B8T261560WW on heatsinks from heatsinkusa. The power supply is an hlg 240 1050b. I noticed on two strips, the lights are dimmed and flashing faintly. What happened?

Just following for the answers myself.

Likely not an explanation. Even the best components occasionally fail. I've seen similar partial failures like that.
Looks to me like one diode completely failed, oddly enough in the exact spot on the board, on both strips.... Inside those strips, the diodes are "wired" together in combinations of series, and parallel mini circuits, that's why a majority of the diodes are still running at full strength, and will likely be unaffected.

You won't be the first guy running a DIY build with a few diodes out.