what kind of light do u have

eh, that thing looks sad ):
how often do you water, and maybe you are feeding it too much? might be too acidic?
or it just might be a runty mc runt runt

I don't think it's over-nuted. the leaves don't yellow like that. They burn around the edges.

I'm kind of thinking along the lines of BudsMcTwill. I actually suspect too little light. But I'm still really new. I could be missing something like nute lockup. I have no idea what that looks like.

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------------------------------------------------------ Growing since 2006.
http://www.rollitup.org/grow-journal...ed=1#post28734

what is your ph at, it should be 6.5 or 7.0 for soil im not sure for hyrdo.If its to high it could case nute lockup

It's severe nutrient deficiency, nitrogen, pottasium and phosphorus probably caused by toxic nutrient salt build up, whacked ph and/or a pot that is simply too small for it's current root nutrient requirements.

Repot it into some fresh soil, a larger pot and give it a good 1/4 weak nutrient flush, and thereafter nutrient feeds at 1/2 - full strength. The plant will be severely stressed as well, use drop or two of superthrive in with the nutrient flush to relieve transplant stress. It will probably add a few weeks to the flowering time while it recovers and gets back on course again.