yellowing to me says i want more N. not a lot but, some. if your organic i wouldnt worry so much about flushing. one or two is usually sufficient. im still saying they are too big for a 600w. you look good for the deficiency though. not to mention plants that size require more nutes, hence your deficiency. the fact they look that good says that eve:thumbsup:rything else is where it should be. good job