having some plant problems... brown spots on leaves

Plant is about 16-17 days into 12/12, it's showing these brown spots on some of the lower leaves. I'm growing under a 600w hps in a 50/50 blend of fox farm's happy frog and ocean forest, in 5 gal paint buckets (2 stacked with a lower one collecting run off). For a few waterings in veg I fed it some "general organics" biothrive grow [light doses according to direction] and switched to light feedings of GO "BioThrive bloom" supplemented with a light dose of GO "bio bud". Using tap water with a high pH, letting it stand about a half day before mixing nutrients and watering... the nutrients seem to knock the pH to around 6.0. pics included... a shot of the leave, magnified front, magnified back, and the whole plant. I looked through some of the galleries but didn't really see a strong match, so I figured I'd ask the world for their opinion. Thanks in advance for any advice you guys may have in the matter.

That looks a lot like mine did with a Ca/Mg deficiency.

I had an inclination of that so I gave it a light dose of CaMg+ last time around, I'll keep it in the regemine unless anyone else has some input.