yellowing leaves white widow

[Slidin.....S15]

Hey stoners

I'm currently half way through the second week of flowering in a cabinet grow. I'm using a 600w lumatek digital with SonT globe with the booster switch on, and cooltube with inline fan to control heat. cyco flower A+B, Zyme, Rhizo, and Potash with EC about 1.7 and ph 5.6 growing in rockwool. Grow space is about 1m cubed

 

Ever since I upgraded to the 600w (had a 400w magnetic before), the new growth on the tops of the plants that are directly under the light are growing yellow leaves. The first week I had the 600w I didn't have a fan connected to the cooltube, and thats when the yellowing started, but has been continuing even with the fan on. To me it doesn't seem like typcial light burn as there is very little heat at the top of the plants due to the cooltube and fan, and the leaves still feel really fresh and moist; they are just a bright yellow colour. As it moves away from the centre of the bulb and the light intensity decreases it goes back to a really healthy green, except for a few spots which are showing yellowing of the leaves too (only on the top fan leaves and new growth). This makes me question whether it is the light, as I would assume that the yellowing would only be confined to area directly under the bulb???

 

I've added a couple teaspoons of epsom salts to my reservoir to ensure that its not missing any nutrients. I think that its related to the light; is light burn related to the heat coming off the bulb burning your plants or is it due to high intensity light burning the plants??

 

I have been foliar feeding throughout the life of the plant and nothing like this has happened; could this be the cause of the prob?

 

Can anyone offer any suggestions on what I could do? PICS BELOW

 

http://i122.photobucket.com/albums/o275/Rafim1985/100_1466.jpg

 

http://i122.photobucket.com/albums/o275/Rafim1985/100_1468.jpg

 

http://i122.photobucket.com/albums/o275/Rafim1985/100_1467.jpg

Edited June 10, 2009 by Slidin.....S15

[thedarkestone]

I've also had this problem. I moved the plants away from the light and it seemed help.

[need4weed3]

light should be about 500mm

from top of plant

[Slidin.....S15]

ok i'll adjust it away from the plants a bit. I thought the whole point of having a cooltube was to control your room temps and so that you can keep the lights closer to the plants?

[need4weed3]

imo its the intensity of light causing the

yellowing

i have the same if the light gets to close

to the tops

if it was the heat the leaves

would be turning brown

and curling up

dont think cool tubes do much

except extract a bit of cash .....

[Slidin.....S15]

^^^^ thats what I was thinking. There isn't much heat coming off the light, and even if it was it would dry the leaves out. So I guess it must be the light intensity.

 

Thanks for the replies