PH damage? DWC troubles...

What do you guys think is wrong with this first plant?

both are BigBud... both are in the same DWC... both are 35 days of flower

1000ppm
GH 3 part nutes per label.
ph 5.6-6.0 (fell to 4.8 for a day is this what caused the damage?)
lighting is two 600w hps and a 400w hps
temp is 78 lights on down to 55 lights off

roots all look great.

let me know what you guys think.

Looks like nute burn to me.....that or heat stress...how far away from the plants are the lights?

well that one was the first to shoot up so it was the closest to the light at about 6-8" for a day then i moved it back to 12"
and my 600s are air cooled so well that i can touch the glass right under it so i'm pretty sure its not heat stress...

could it be from too much light intensity?

is it strange to have one clone thats able to handle higher nutes then the rest?

when i've ran DWC before i've always had the same problem on all the plants.

either way i will flush and refill soon as i get my nutes in... i'm out.