1 plant looks dead with pic

I currently have a 4x4 area 7' tall, well ventilated, running 700 true watts of CFL light. I grow 6 plants at a time, and monitor them often daily. One plant has dumbfounded me. It has curled down leaves with brown spots. Plant has had the same soil,water,nutes, everything as the others, but is not doing good. It still has decent trichomes, so I have kept it going for medibles. Just wondering if there were any thoughts, as I have tried everything. N - defficiency, over water, under water, I have flushed, and nothing. Trichomes are still clear, so I still have time to treat it.

Looks like a disease of some sort to me.

I'd guess nutrient burn, major. The leaves are dark green (too much N) and the tips are burned to a crisp. I'd say heat and airflow may be coming into play there, but CFLs are pretty cool. Of course it could be a virus, hard to say. I was paranoid about the tobacco mosaic virus so I don't even smoke near plants. (bad habit anyway)

If I had to guess, I'd say root rot. It looks like it can't take up moisture or nutrients. Just a guess, though, from looking at one picture.

What is the strain? Is your whole grow the same? As all of your girls have been raised the same, it could be a genetic flaw in the one seed. Or perhaps as previously suggested root bound.