Dead leafs!!! Whats going on????

SUPER LEMON HAZE INDICA PHENO its a hydro grow 400watt hps pH 5.2/6.1 EC 1.3 nutrient temps 22c room temp lights on 25c/28c lights off 18c/21c
The bottom of my slh is not doing too good by the looks of it the budding is 3 weeks in of 12/12 not sure how they look the plant is now 9 weeks old from seed 6 weeks veg and now 3 weeks flowering. I have just pinched 3 small branches looks like the first branches because the leafs had dried curled so very dead don't know why advise needed take a look
[video=youtube;rLAfMIFOFyQ]http://www.youtube.com/watch?v=rLAfMIFOFyQ&feature=youtu.be[/video]

I have the same plants! 4 slh but in soil its doing a similar thing but im at week 4 flowering, Im not sure what its doing but would like some advice.

Super lemon haze is sativa dominant therefore has a long flower time. Your just getting into flower with her at 3 weeks. From the looks of some of them leaves in the video you seem to have some eagle clawing going on. Too much N. Check your ph and ppm again just to make sure then lower that N! Too much N in flower will definitely claw your leaves and if not fixed will burn them till they get crispy and fall off and will stunt growth and flowering.