Is it ALL the blue LED's (in one fixture), or just a few here and there.
If all, I would most certainly check the cable or connector that runs to your LED board. I have noticed a few manufacturers like to zip tie everything on the inside to keep it clean. In the process they make the strain on the connector so tight, it gets partially pulled out during transport. Just a thought..
If its only a few LED's, the lights I use have a similar problem, but with Red:
A strange thing I have noticed with the pars I use is a single LED will fail and leave the rest of the LED's that are in the same series branch working. When I was replacing the individual LED's I would often leave the light on while removing the LED (not safe, blah blah), but I noticed when I heated up the pad with the soldering iron, the LED would spark on and would work as if I had just fixed a cold solder, or bridged a gap in the connection. I at first thought it was a solder problem as the fixture was cheap, undoubtedly from China. After about 5 minutes I notice the same LED flicker out, and stopped working again...Strange. I removed the LED entirely and cleaned the pads and began to solder the LED back into place. It popped on again....and after less than 5 minutes it was off.
Strange but what I think is happening is the diode failed (manufacturing?) and partially shorted, allowing current to flow through to the other LED's (And for some reason drop close to the same voltage). While hot, the LED would emit light, while cold...nothing).
