Leaf problem

[justanotherbozo]

I grow indoor on Special Mix Light soil , no fertilizer during veg state (4 weeks).
I've only added a slow release buffer-tablet and some Bacto
I use plain water ph 7.8 and cannot measure EC
The plant is grown from seed and is 4 weeks old.
Lighting source and distance from plant: PL-L 440W, distance 1-2 inch
Air temperature 22/27
Relative humidity 45-50 %
Lighting schedule 12/12
Only this one shows the problem other plants (10) are not affected
The stains are more orange irl then on the picture
http://gallery.wietforum.nl/12451665...7779_15023.jpg

it looks like maybe a ph problem although i'm no expert.

7.8 does seem awful high too. ...take a look through the link in my sig, Stitch really
knows her stuff!