Plants started having problems

I have started four new plans in a new hydroponics flood
I am having a problem with the plants. They started off good and they just started going south. Here are a few pic's ...
I am using the advanced nutrients grow A & B
In the pic of all the plans the one in the front on the right is not being affected so I didnt thank it was chemical burn. The other three are all doing the same thing. I am feeding once every 4 hours for 30 min they are all in rockwhool.
The second pic is of a plant in the same grow but I am not seeing the same affects out of it

Looks like you have some type of nutrient deficiency. Go read the sticky on the main marijuana plant problems forum.

... Whats your PH fluctuations like?
How often have you been doing a Res change?
Whats the ppm of the Nutrients your using?
How old are they?
Are you only using A and B?
What type of Hydroponic system? im assuming ebb n flow since you said 4h for 30 mins (im telling you now 30 mins is too long) would be better for 15 mins every 2 hours, but thats not your problem.

Notice your leaves are curling up on the edges. There trying to transpire water vapor because of one of many problems.
What size light are you using?

Answer these questions and ill solve your problem! Promise!

Im banking on PH Nute lockout or you havent changed your rez!

(Ps: If I help you owe me a like )

I second the notion of a nutrient deficiency. When I first started bubble buckets my main problem was a cal-mag defiency. Intervienal choloris of the lower leaves along with stunted growth/ small leaves could also indicate a zinc/iron deficiency. Weed loves cal-mag and iron, and most hydro nutes lack this. especially if ur running distilled water. I would recommend foliar feeding 5.9 pH distilled with ,5 tsp/gall cal-mag and dump the bucket. aim for a concentration of 100 ppm Nitrogen, 80 ppm phosphoprous, 60 ppm potassium, 30 ppm iron, and 80-120 ppm calciium and magnesium. For any major nute company they have calculators on their website so you can tailor the exact concentration of nutes. HYDRO is a SCIENCE not an art like organic soil. Think "scientist" in hydro mode and "hippie" in soil LOL.