Scary dev just to make clear the leds will be damaged if overvoltaged.
A led marked at 1.5 volts operates normally at 1 volt goes up to 1.3 volts
good diodes can handle twice the voltage for short periods but goes greenish after a while
try them at just 25x voltage and they blow up (really blasts) in 1 sec or go greenish to dark. At 50x voltage instantly blasts
checked using volameter on diffrent leds flat sphere square and the ones on strips.
Next i would be checking my 5610d dual led flash

if you are intrested you will get the report a day after or two as m offtown