OK. I had just had the same 3 leds turn off like the OP posted. And since I am now past warranty I decided to investigate and it seems I found out what is causing this issue.
PROBLEM:
If you look at the back where all the wires are, you'll observe that those small black connectors are cramped/shoved inside the small hole, exactly where the leds seem to be having problems (hint!). So I believe one of those connectors is constantly hitting the part where the led is soldered on to the board
(the affected led is the first led you see when looking directly in the hole) and over time, that solder will eventually come loose and cut the circuit running the other 2 leds.
SOLUTION:
1. FOR THE OTHER PAIR THAT STILL WORKS:
I suggest you start getting those black connectors out of that hole ASAP!!! The wires have a bit of a slack to them so you can carefully get all 3 out of 4 connectors out.
The one with the BLUE WIRE seems to be short so leave it inside. Now you can tape/clean up those connectors outside the hole and call it a day.
2. Unfortunately for the busted tailight, you may have to open it up. There maybe tutorials on the DIY thread or on youtube on how to open headlights. Same concept applies here. I would suggest the baking-in-the-oven method. As for the soldering part, youtube is also your friend.
UPDATE: If you have steady hands and is good with a soldering iron, the hole is big enough where you can just get away with heating up the connections and getting enough lead in there to attach it back to the board.
GOODLUCK!!!!!!
