Looks like a PH issue/nute burn... I'd back off the nutes, check PH and flush... wait a few days to see if newer growth has any necrosis....
FAQ...to plant problems...to PH/nute prob. ..... to chart by Neitzsche (has pics).... Luck.
i looked at the thread and that is what i am thinking a cal/mag def!! i had a bug problem! those little gnats, and i got rid of 99% of them i see maybe on flying around how can i fix the mag def
Mate your ppms are of the chart! If you have a Hanna tri-meter it is most likely set to .5 or .64 conversion which would be a EC of above 3.0 at least.
If you don't know how your strain behaves you should never be above 1.7 EC or at .5 conversion 850ppm, and on .64 conversion 1088ppm.
I would do a flush until my run off EC was down to no more then 1.0, then refill with no more then 1.7. They are not going to like the fast change but you are to far from finishing, I fear they will burn before you get there. Happened to me last grow