2 weeks into flower, leaves yellowing.

Grown in soil, they are 6 month old mother plants. kept very short, at 2' going into flower. Heavily tied down. anyhow, these are about 16 days into flower, and they are yellowing. Mostly older leaves yellowing, but 1 of them has and over all pale look. There are 4 plants under the 1k HPS, 3 are bubba kush, and one is a strain I grew from seed given to me by the teacher of a grow class I attended, I cant remember what the name of it. they are in 5 Gal soil pots, being fed the entire general organcis line ( got it as a free sample, big bottles though) so far, the first few feedings have been on the "grow" diet so i dont understand why they are yellowing. Any ideas?
http://www.flickr.com/photos/21535047@N05/

Looks to me like a lack of magnesium

" Magnesium is a component of the chlorophyll molecule and serves as a cofactor in most enzymes.
Magnesium (Mg) deficiency.
Magnesium deficiency will exhibit a yellowing (which may turn brown) and interveinal chlorosis beginning in the older leaves. The older leaves will be the first to develop interveinal chlorosis. Starting at leaf margin or tip and progressing inward between the veins. "
justatoker

themistocles said:

Looks to me like a lack of magnesium

" Magnesium is a component of the chlorophyll molecule and serves as a cofactor in most enzymes.
Magnesium (Mg) deficiency.
Magnesium deficiency will exhibit a yellowing (which may turn brown) and interveinal chlorosis beginning in the older leaves. The older leaves will be the first to develop interveinal chlorosis. Starting at leaf margin or tip and progressing inward between the veins. "
justatoker

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its starting 2 get nitro defiant add some veg ferts next couple of feedings 50/50 veg/ flower

pinkjackyle said:

its starting 2 get nitro defiant add some veg ferts next couple of feedings 50/50 veg/ flower

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not magnesium. its nitro, its just cause ur starting flowering. 20 mg of cal mag will fix it instantly, but its not really nessasary, alot of plants have yellow leaves and huge pretty buds its just flowering.

x3gop1yr said:

not magnesium. its nitro, its just cause ur starting flowering. 20 mg of cal mag will fix it instantly, but its not really nessasary, alot of plants have yellow leaves and huge pretty buds its just flowering.

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Thank you all so much for the replies.
Like I said, I have been giving them the GO line, including the camg,

(I am using mostly water from my Dehumidifier to water them, so they deffinatly need the camg).

So if it is N, am I safe giving them another feeding or two of 50/50 Veg/Bloom ratio? They are alreay about 2.5 weeks in. Will I be risking not giving them enough P?
And again, thanks a lot for the help. Learning everything by trial and error is a hud PITA, I appritiate having fellow growers out there that will take the time to help people out.

And now they all have pollen sacs... all four of them. One was way worse then the other three, i chopped it. The others I picked off all I could find. I am thinking mabye I should just chop them as well. its such a bummer, these were vegged 6 months (they were mothers)