Appears healthy but exhibits slower growth

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Update:

pH in the reservoir is sitting happily at 5.9. No drift. No swings. I'm a coco convert, I think. What issues are common in coco? What should I be looking out for? I feel like this is going too easily and it's making me concerned.

The BESTVA p1000w appears to be providing enough light to all three plants. Dream Queen is a smaller plant according to Homegrown's grow profile:

"Unlike many Sativa-leaning plants, Steve's Dream Queen only grows to between 3 and 4 feet tall. It produces small, dense buds tightly clustered together in a typical Indica fashion, and its flowers are covered in striking, rust-colored pistils and milky-white trichomes. The buds have a sticky texture and a glistening, vibrant appearance that helps them stand out against the pale green leaves."

I've moved and tweaked the light to favor Dream Queen, thinking that it wasn't getting enough but now wonder if it's just the genetics?