From days long gone by, I seem to recall that the most likely failure mode
for diodes in general, of which category, LEDs are one instance, is to open
circuit (burn open).  The lighting result in this case is the same as
breaking the circuit.  All LEDs in the series branch switch to dark mode.

Most diodes are limited by power dissipation.  When they get very hot they
cannot dissipate the power across the junction and the junction temperature
rises until the diode is destroyed (generally to open circuit).

Now back to your regularly scheduled programming.