Whats wrong with these, any help??

hi, im new to forum as a member but i read lots of material on growing indoors before i set up this 3.5x3.5x7 grow room in my second floor attic, (not the roof attic), temp during the day is about 85-90 and night 75-81, i have to (1) 260cf air ventilation that brings cool air from outside every 2 1/2 hour or so set on timer, and another 260cf fan that blows out the air from the grow room, both fans are on same timer. plus i have $15 18inch fan that i use inside to keep the air circulate, now for my system i have 28 gallon aeroponic reservoir, a decent water pump with this custom sprinkler head on that i thought would be good 360 flow for my system, a decent air stone pump that runs 24hr, i have 6() 6'inchs pots. i germinated my feminized white widow seeds on september 19th, they sprouted on 21th, and 1inch seedlings on 23th, since then till today (october 18th) my plants were looking healthy except 16 hours ago i start to notice some yellowing on the leaves, and its only gotten worse and this is the recent pics i just took few mins ago. my ph is 5.79, ppm is 620, m using Auqa Vega A & B nutrients by canna brand, and water pump is 15min on 45min off, 18/6 light cycle from 150w HPS bulb.

sorry for piling up all the info in one paragraph but i jus wanted to give background history, anyways please help me with my situations and need smart guess on what could be wrong wit my plants, i read about all the deficiencies but i still feel kinda confused and i have no clue how i can treat this, my request to any old timers to guide this noob with wisdom of knowledge, thanx any help is appreciated.


HERE IS THE PICS OF MY PLANTS & my grow room!

Cal/mag def...U can use micro nut for help your plants ....

okay thanx, ill try to get this: http://www.texashydroponics.com/shop/product.php?productid=1832&cat=0&page=1 from my local shop and hopefully this should treat if your right lol