EASY KILLER.. EASY...

interestinig that it is that one plant that is so bad.. Can we see the roots..? there is a chance that the resivoir got warm an d the roots are rotting.. although unlikely this early in its life...

It does not look like nut burn... although 1350 seemms high for such small, young plants.. unless your fert is weak, that is HIGH!!

actually, I just looked at all your plants and none of them are doing well.... you need to clean out the resivoir... and refill it.... set PH at 6.5-7 and ppm at 600... If you can use distilled water....
this wil give your plants to recouperate from whatever they are going through... If it is not root rot, they will be fine in 3-7 days and you can increase the ppm to 1000...


deep breath

i love you