I'm almost in my 7th week of my first grow. I'm using a 2X2 ebb and flow table with rockwool cubes in hydroton pebbles inside a 272 cubic foot room. I'm using a 600W HPS that gets cooled by an 8" inline fan pulling air through the reflector and the temp stays around 70-80F with 50% or so humidity. I flood the table every 6 hours for 17 minutes with tap water that I PH balance after adding General Hydroponic brand nutrients. I just switched over to flower stage about 2 weeks ago. I don't have a PPM or TDS meter, just some PH drops and the feeding schedule from the Gen Hydro web site. I've got 4 different strains growing, but the problems only seem to be on the Afghan Kush (indica) and Blockhead (mostly indica). The light is about 12-18 inches away from the problem plants, but there are two Smurfette Fantastic (don't know what strain, dude forgot so I made it up) plants that are about 3 inches away and not burning or curling at all. The Blockhead does have some Spider Mites that I'm spraying with Neem Oil every three days to try and get rid of them. The Blockhead has light green almost white new growth with dark veins. It's not the whole plant that looks like this, just some of the new growth. I've got some pics, but since I am in flowering stage I couldn't go in with the lights off so it's hard to see. The Afghan Kush has a pretty bad leaf curl problem. They are curling downward and the tips are turning brown and dying. And again it's not he whole plant that is doing this, just mainly the tops. The other plants seem to be doing fine, except I'm worried that one of the Smurfette Fantastic plants is showing signs of leaf curl (attached pic). Any help would be great since I want my first grow to be awesome!