Cant figure out whats going on..

Well I seem to have my environment pretty much under control. I just cant figure out why my leaves are drooping...

Im running deep water bubbleponics..

PH:6.2
Air temp: 70
water temp: 68
humidity: 60-70%
ppm: 750

Plants are at week 4 from seeds.

Sounds like you got it down man. A little high on the nutes but by the book.
Ya know, just by lookin at the pic I would say its over watered. Your roots have hit water right?