I had a similar problem that Stinky helped me out with. Yellow and dry with the edges curling up. It was a combination of Nitrogen burn as well as underwatering. I would suggest, as Stinky said, to flush twice and test your soil with a Pot/Nit/Cal test to see what you need. Go easy on the ferts so that you are not back in the same boat.

My experience is that you are better off under feeding than over feeding. They may grow slower but they will not get burned. Everything new that is introduced needs to be slowly too. When under new lights, when adding fert as well as LST, etc. Too many people rush the process and stress the poor ladies out. Slow and steady winns the race.

BTW, thanks a million StinkyAttic. Blueberries are being LST'd now and are incredibly bushy and greening up nicely! I am used to Sativa strains so the thick leaves are a trip. I flushed and am doing a soil test tonight. They are already incredibly pungent and I only started them on the 10th of Jan!