rust spots getting worse (pics)

OK, hoping someone can help. These plants are 35 days old (day 28 of 12/12). I am using the Advanced Nutrients 2+ Bloom (medium feeding) program. I continually give them 2 feedings of nutrient (at 6.3ph) and 1 feeding of regular water (at 6.3ph). I foliar spray with Growth Excel just before the lights come on about 2-3 times a week (tho I dont PH the water I use for this foliar spray - should I?). They are growing in ProMix HP under a couple of 1000 w HPS's. Temps are between 17c/65f and 26c/83f. Air circulation is good. Humidity is not a problem. Starting at about day 20, I started to notice rust spots on some of the leaves. It got progressively worse day by day. I started reading/asking around and came to the conclusion that it was most likely a defiency of calcium and/or magnesium, so around day 27 I gave them Cal-Mag plus (5ml/gallon). I have since given them the Cal-Mag of 3 of the 4 waterings since but the problem seems to be spreading (from the lower leaves up). I tested the runoff of my soil on a couple plants. Using nutrient water at ph 6.3, I get a runoff of 5.0-5.3. I beleive this is too low. Am I right? Does this have something to do with my problem?. Is there something I can/should do? Any ideas would be appreciated.

stop using growth excell. it looks like spray burn, like when you mix safer's too strong...

Thanks for the reply. I suppose that is entirely posssible, BUT...something I meant to mention. There are some plants among the others that seem almost completely unaffected by this problem. Most, BUT not all, are of a different variety. Also, in almost all the cases, the problem has started toward the bottom and moved up the plant. If it is in fact the Growth Excel causing the problem, than why are the tops OK?? Just a thought. Again, thanks. Any other ideas would be appreciated.

ok, check on the temps, and check for spidermites... could be a heat prob...

so.... i've got to find that damn leaf chart...

love, kp:p

Plant Abuse Chart

Bookmark that link, it is a life saver (for your plants)

Quote:

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Originally Posted by Splifted

Plant Abuse Chart

Bookmark that link, it is a life saver (for your plants)

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damn big props on that link... that shit looks very usefull..

Your pH is way too low for dirt.
Get the soil up to 6.8.
Flush!
Water with a little higher pH water than you want ... so like 7.5 for a couple waterings... test soil runoff again

OK. Thanks for all the replies. Kindprincess, I do not think it is spider mites. I have been checking them closely every day or two and see no evidence of them. I will continue to watch. Like I said, temps are peaking at 83f/26c, which I dont think is any problem. Splifted, I had and have again checked the plant abuse chart and the plant that closest resembles mine would be the magnesium deficient one in pic 16 I think. Stinky, thanks for your advice too. I knew the ph level of the soil was screwed up. So, lemme get this right. Flush with plain water (at what ph?), THEN water with ph7.5 (after they have dried again I assume)??. OR do I just flush with the high PH water?. I'm a bit confused on that one. Thanks again to everyone.