What does this plant need?

Hey guys. Having the hardest time with my grow this time around. Have had 3 very successful grows, but right from the beginning I have had an issue I can not seem to solve.

I run a simple bubblebucket hydro setup. 2 buckets. 45L air pump with ceramic diffuser stones. Running Aqua Flakes A+B and Drip Clean. Very simple. Temps are great, humidity is great. PH and PPM seems to be right on point. (PH meter is a year old, was thinking of replacing the node, but it still seems to read true when calibrated).

But no matter how many times i have emptied and cleaned and started over with these buckets (using RO water as well) I can't seem to stop what you see on the leaves in the pictures below. But the plants are growing heartily. The plants are about 6 weeks old, running 24/0 light, 400W HPS in a cooltube. Growing a Blueberry Gum and a Kushberry this time around.

So anyway, i need some advice. What do you guys think is the cause? Thanks for reading. Peace.

anyone? surprised to see 47 views with no suggestions.

Really? No one out there can diagnose my leaf?

do u have pics of whole plant.

Why does the whole plant matter? I have leaves like pictured above, and healthy green leaves. Plant is 6 weeks old in veg, and have been getting leaves like above since the seedling stage. I got into a motorcycle accident saturday and broke my leg, so I really can not get into the area to take good pics, so I figured the leaf would do just as well. I put as much detail as I could in the description above. Very simple setup, with good #'s all the way around, except for the leaves that look like above, and I have no idea why.