Yeah that's fucked. Throw it away. 15 days from sex? You'd be better off starting all over. Here are your realistic options.....let's fast forward to 8 weeks from now. You could have a brand new plant that is happy and healthy about 3-4 weeks into flower and doesn't look like shit and isn't dying and making you want to punch a wall everytime you see it OR you can sit on this piece of shit and hope it comes around. Why waste the 8 weeks? The only thing I MIGHT do is pop some new beans or get some new clones (whatever floats your boat) and in the meantime take this plant and put it somewhere. Don't water it, don't do shit to it and see if it bounces back. After a few days if it bounces back it will give you a more definitive answer as to what's wrong so you can avoid it NEXT time.
It doensn't look overwatered to me, looks to me like you nuked the shit out of it with nutrients and it went and locked everything out. I'm a pretty decisive guy, but I'd probably kill it now, tear it all apart, look at the roots and see if they are rotted. If they are it was overwatering, but more than likely the roots will look okay.
I'm not trying to flame or come off like an ass, just trying to get you to see the big picture 8 weeks from now.