Spotting! beginning fourth week.. HELP!!

[johnkramer]

The spotting problem begins on the 4th week, starts in lower middle fan leafs and progresses to all of the major leafs of the plant. 'They become dry and brittle.

Following is a description of lights, temperature and other relevant facts.

Irrigation: ebb & flow
resevour: 22 gal
R.O. water only
PH of water: 5.5 ( I try to keep it at 6.3)
Water temp: 69.7 fareenheit
Water changed every 7 days
Light: 600 w HPS
PPM of nutrient solution: 857 PPM
Tray dimensions: 4ft x 3 ft
20 plants per tray

Nutrients
@ 40% of recommended strength 1st week
@ 50% of recommended strength week 2 thru 8

Monster Bloom
Botanicare Pure Blend pro 2.5 - 2 - 5
Sweet
Liq Karma
Cal Mag

At water replenishment I add Sweet, and cal mag

[bio1]

It looks like a nutrient defficiency.

Well. Im not a hydro grower but maybe with this site you can find out what kind of nutrient burn it is:
http://www.icmag.com/ic/showthread.php?t=11688

[ganjaganja]

check out ganja guerilla's website, he has a list of nute deficiencies, which is what you have, that you should check out, they are pics.]

just google his name