cold water hydro

i have a flood hydro setup and all has been going well untill i accidently ran a cycle with cold water 3 weeks ago.some of my plants roots turned brownish not all of them.the cold water was a rinse with straight water for one day then i went back to the bloom food. my plants look like hell basically they have not grown much for 3weeks and there is yellowing of leaves and my flowers thinned out they were very dense n fat now they are thinning even getting lighter. i got leaves turning yellow and their stems are reddish purple.

i put some new plants in a week after the coldshock incident and their leaf stems are turning reddish.
i would like to know whats happening i need help.:smokin:

What's your ph?

...of the HUNDREDS of details you could offer, that's where I'd start lookin' first!

the ph is 6 in that general area ,its the same its always been i dont need to adjust the ph at all.the system is a flood setup w/25gallon res. the flood tray is 2x3 ft.it runs 3-5 cycles per 34hr. one cycle takes 10-15 minutes and it floods to the surface of the cubes.lighting is 250 hps x 150hps. ambient air temps are perfect 71-74. when i spray them i spray a very fine mist about 2hrs after the light goes on,i apply 2-4 light mistings on days i mist.

i was thinking it looks like a nitrogen is to low.i just emptied the rez and refilled it with water after it gases off and gets warmer im gonna use a plant food with more nitrogen.

water temps are average 69f-72f