Hard to say. 6-6.5 ph is a little low for soil. Which ones are the WW?...are they in better shape?...or worse?

Have you transplanted lately?...I'd do that first, and 24 inches might be too far away?...try 15-18 inches with a 400 watt light. The leaves are sucking out too much nitrogen this early? I'd lose those drip trays, too. Must have good drainage away from the pots.