DWC help!

Im growing 3 vanilla kush dwc flora duo nuts part a+b 600watt hps ppm 600 pH 5.5 temp 72. Just increased notes past few days from 350-600ish ppm. The largest once healthiest plant is now curling its margins downwards which us to much N it low pH correct.

yes N will lower PH and yes that is N making the "claw" downward hook. I hope you are not running all that fertilizer for 3 plants of various age. You are destine for problems.

Dude, way too much for such young plants. More is not better.

I agree I back of nutes with fresh refill and noticed my timer was stuck in on position 24hours. I'm thinking a little light stress too.I'm a bone head.

600 PPM is wayyyyy to much for such young plants. In hydoponics it is very very easy to overfeed or "burn" your plants, but very seldom do you see underfeeding and not enough nutrients. Rule of thumb, whatever the measurements on the back of your bottle say, just use half strength from what it says. If it says use 2 tsp per gal then start with 1 and work your way up from there. It is also very hard to recover from nute burn but very easy to fix under feeding.

especially the deep water culture because the roots always sitting in nutrient solution. You can run a little lower PPM's you normally would

What kind of air pump and air stones do you have in that tote?

600ppm is not too high.

Those leaves are curling under from low turgidity, which is definitely not from nute burn. Nute burned leaves are too turgid to a point where they're crispy.

Leaves with the claw are distinctively different from larger leaves with downward curling margins. Leaves with the claw are generally the newer leaves and have a certain firmness to them. Your curling leaves look old and flaccid. I'd actually up the nutes.