Brown marks on leaves-1 1/2 week old plant...

Hello guys,
Vitalink plant start -currently 15ml/10L tank, recommended dosage by vitalink is 40ML.
Ph 5,2-6,2.
PPM-527
Temperature of air- not higher than 26C.
Temp.resrvoire-21-22C
This my first hydro grow and thus i'm lost.Can somebody tell me what is wron with plant,pls.
Second plant have allready brown root


Isn't that a root rot???
It looks to me that my first grow is allready starting with troubles....

Thank you very much for any help
SORRY for posting in wrong forum section-modes please move it to hydro grow.Again sorry :-(

Hey bro I notice in the pic that water is pouring out of the net pot like it was underwater and you just pulled it out for the photo. I don't do dwc/swc whatever it is you're doing there, but I think your net pot should be above the water line at this stage. I would look into it.

Check out Lysol's sig for a great thread on slime/root rot/algae and the eventual cure, Physan20!