The blanched tips on new growth indicate nitrogen overdose. And barring any new photos I am going to venture a guess that you have caused nutrient problems by overfeeding, incorrect pH and poor air movement. Looking at orange pics sideways . . ..Any chance you can upload a picture that isn't orange from your light? Bring it out of the grow area, that way things will be easier to see as all the leafs just look different shades of brown under the HPS light
Given that they're starting on the lower leaves, I'd say it's nitrogen deficient but the colouring in the pictures are a little "tango'd" =]