dam looks like a food issue, but with feeding twice a day i dont understand how that could happen.. maybe try feeeding just one a lottle more n see if it greens up. its showing signs of a sulfur deficiecy, but that is normally caused by nutrient lockout or a high ph so that shouldn be the prob. its jus wierd how it covers the entire plant. im sorry bro i hope you can fiigure out a solution.