I am building a high-powered flashlight using four Cree XHP70.2 12V LEDs, but just after the final assembly of the flashlight, they all started malfunctioning in some way. See the images:
One LED is is half bright and half dim along a diagonal:
Two LEDs are half lit like this one:
And the last LED does not light up at all. These are images of the whole assembly (with reflector removed):
All of that gray gunk is insulating thermal paste. The blue dots on the corners of each LED are beads of silicone glue (in an effort to prevent short circuits through the exposed corners.) All of the LEDs are wired in series.
I've checked every combination of leads, and there are no short circuits. There is also no conduction between the leads and the copper bottoms. All of these LEDs used to work fine. My best guess is that I somehow damaged them with excessive pressure after mounting the flashlight reflector on top.
Are there any better explanations for why each LED is acting the way it is? How can I fix whatever damage has been done?
I tested each LED on its own, and they all work properly. Somehow, the combination of all of them on the aluminum plate messes things up.