Back to the 12/12 Stage

These are the specs.

12hours HPS light/12 hours dark
70% soil+30% vermiculite (worm casts included)
Been on veg for 3 months (before the 12hours)
Water pH 7.0
Soil ph is between 6.2-6.8 (tested with henna tester)

Now this is what is happening
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Those are pics taken lately. The only fert ive used was 12 days ago. It was a 10-30-10 used at 1/4 strenght. I have made it 1/4, but im starting to believe this is a nute burn :S Leaves get brown, and then curl up. This happpens first in the low part of the plant and then goes slowly up. BTW i have placed 3 of them in 12/12 and two of them are showing these problem. The other one is flowering very fast, while the sick ones are not even showing too many hairs yet.
What do you think?
BTW this already happened to me once and ALL the crop died so...im pretty stressed right now :( a little help would be usefull. If you need more specs ask me, il check the forum constantly.
Peace