Hey so I am attempting my first grow and I am using the space in my closet. I am growing 8 plants of some grandaddy master kush. I am using grodans and a 400w light. It is in the grow stage right now and the light cycle is at 18/6. I water them once a day and I am having some issues. I started with 510 ppm's then moved to 640, then moved back down to around mid 500's. The plants don't seem very happy it looks like nute burn and I decided to flush the plants for 3 days but still don't seem very happy. The stems are purple and the leaves are yellow, lime green, and brown. I am asking if anyone would be able to tell me what I can do to turn these plants around. Thanks!