Leaves go down every day

Help I need to know whats wrong.
I have a blue hash plant its 4 weeks old and around 12 inches high
In 100% coco Using General Hydrophonics nutes. I mix nutes at 5.o ph < is that to high>?
I had been watering it too often and i notice the problen and only water every other day.

But still every day the last few hours of the light being on <18/6> the big fan leaves start to droop down , then the next day after ligths come on they are all standing up reacing for light. 400 hps around 20 inches above the plant

what could be the reason the leaves droop every day.

ps Ihave a cheap o combo meter in it got at wall mart for soil
and it says the ph i high. but if i take a hand full of coco out an squeeze
the water out of it its ph around 5.0