The LEDs in your lighting fixture are wired just like your Christmas lights. Meaning they are connected in series just like a chain and when one bulb or diode goes bad, the whole string will not work. However, instead of a 120 vac that powers your Christmas lights, the LEDs normally use 24 VDC or more. It is easy to find out which one is bad without using a meter. Just get one dry cell battery 1.5v and attach a piece of wire at each end wrapped with an electrical tape then tap those wires to the LED
one by one according to the LED
polarity. Reverse the wire if it does not lit at first then follow the same with the rests. Good LED
will lit and the bad one will not. Each LED
will have maximum brightness with 3 volts across.