Help a good guy out lol

[browneyes1888]

Hiya guys been having issues with done Dutch passion white widows autos
Growing in 10 litre airpots of plant magic soil and following tangs guide on an nutes
Done this for last few grows an it's been great but once I get too day 30-40 the plants go to shyt with wot looks like major calcium def
Temps have been 28 degrees
Run off is ph 6.8 and ec2.0
Leaves are going crispy and curling up tge way from bottom of plant upwards
Growing under 600 watt hps
Here's some pics or major crispy leaves and brown rust

 

[Trapper]

Run-off is 6.8 what is the solution pH going in?

What distance is that 600W ups away from the very top of the plant?

 

[browneyes1888]

Run-off is 6.8 what is the solution pH going in?

What distance is that 600W ups away from the very top of the plant?

solution going in is 6.6-6.7 and the distance is about 15 inches from hps but its air cooled hood and also fan going on and off between light and plant tops

 

[Trapper]

Okay....so your pH is a little high.....



in 6.6 pH and out 6.8 pH means soil is 7.0 (difference ADDED to the run-off) but not seemingly crazy....

RE: The light - The heat may not be an issue (I assume you can hold your hand at the top of the plant and not burn your hand holding it there for 10-20 seconds)
but the intensity may be another matter....15" seems reasonable but what do I know...I'm LED-based.

Wish I had the answer, Brother..... Good Luck!

 

[fweedom]

looks like some heat stress going on (could be wrong i cant click on pics so its hard to tell). When i got high temps the leaves would curl up like that and after i put more fans on them for better circulation and lowered temps the leaves straightened back out so if ur at around 82 degrees that could be part of it :Sharing One:

 

[faded187]

manganese. from too high soil ph. MHO or lockout from some other overfert

 

[az2000]

Potassium deficiency. Unrelated to your PH (if it's really in the 6.8-7.2 range). See http://growweedeasy.com/potassium-deficiency-cannabis for photos of similar.