Check this thread mate: http://www.icmag.com/ic/showthread.php?t=11688 Not too sure what it is as I'm no expert...it also looks sort of like plastic offgassing as seen in tents. http://www.icmag.com/ic/showthread.php?t=103659
Hope you find a solution
thanks. i think it was from my nute mix running hot. things have stopped burning since i lowered the strength of my mix.