6th week, F&V auto

Need any info on this,please. They are 6wks, fast & vast. Good soil, bacteria water,no nutes. Why are the leaves yellowing? Also,what's the difference in HPS and CFL in terms of yield and electric bill,if anyone knows. I use CFL right now.

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I can't see the CFL in the photo so i'm assuming it's furthur away. If so you need to get those bulbs really close to your plant canopy. How many watts are you working with???