Need help with this

[leca]

Repotted this plant about 10 days ago into a 50/50 mix of average strength compost (its basically a good brand of soil with 1.5dl/25L bone meal and 1.5dl/25L dolomite lime in it + about 15% perlite, 10 dl = 1 L) and "seedling soil" after it got a way too strong feeding and started to show nute burn. At same time i took a bunch of cuttings off it to save the growing tips from the nute burn and flushed the old rootball with R/O water before potting it up and about a week later first root could be seen coming out at the bottom of the container. In general the plant has made a very nice recovery from the nute burn.. however last few days another problem has started to emerge.

Grow details:
Light been on 20/4, temps at 25-30C and RH 25-40%. Ventilation is, to put it mildy, adequate for the size the grow is in at the moment. Lightning wise its been ~50cm (~1.7 ft) under a 600W HPS except except last few days where its been ~30cm (~1 ft) under a 250W HPS.


Random thoughts:
Since the problem seem to affect fan leaves all over the plant it shouldnt be the classic 'one fix cure all' MG defiency, also i really dont see how the plant couldve used up all the nutrients in the soil yet. Infact, its definately worse the closer to the top of the plant you get.
Likewise, i find it hard to believe its a micronutrient problem caused by the R/O water not supplying any then again im not entirely sure pure R/O water is suitable. Is it? Could the added dolomite lime be causing problems?
Or is it as simple as me giving a burned plant too much light?
Even worse, could this be some fungal/viral infection?

Should also say at this stage im not feeling very comfortable in giving it a feed, was really hoping to go atleast another week before starting that.
The only thing ive done to change the above situation is move it somewhat further away from the 250W HPS giving it a pretty low light spot to hopefully get better in.

Any experienced help greatly appreciated, be it specific nutrient problem hunches or changes to my grow methods :)

[vapor]

looks like it needs some nitrogen .,how wet do you keep your soil?

[leca]

looks like it needs some nitrogen., how wet do you keep your soil?

In my experience nitrogen def doesnt affect the top fan leaves the most, rather the opposite. The intervenal chlorosis in the 5th picture has happend very quickly over the last few days. When it was under the 600W soil got a good watering maybe every 3 days (quite hot in that room) and while under the 250W maybe ever 4th. I've been pretty carefull to not water it again until it dried out (not just the talking about the top of the soil here, lifting the whole container to get a feel for it. As reference i've done 500g/600W harvests before and the plant has'nt been overwatered.)

[vapor]

http://www.marijuana-seeds.net/Thanks/ThankYou.htm

[c-ray]

looks to me like more of a potassium deficiency and a magnesium deficiency...green veins indicate that there is sufficient nitrogen
looks like the plant is sucking potassium from the leaf margin edges because it is not available at the roots
a shot of kelp (or another good potassium source) and a dash of epson salts might help, try the kelp first and see what happens
how is the pH of your water, and the pH of the water that is flowing out of the pot? a pH below 6 will reduce the plant's ability to uptake these elements

[c-ray]

also your temps are a bit high, if you can lower 5-10 degrees that would be helpful
and also how dry are you letting the pots get between waterings?

[leca]

looks to me like more of a potassium deficiency and a magnesium deficiency...green veins indicate that there is sufficient nitrogen
looks like the plant is sucking potassium from the leaf margin edges because it is not available at the roots
a shot of kelp (or another good potassium source) and a dash of epson salts might help, try the kelp first and see what happens
how is the pH of your water, and the pH of the water that is flowing out of the pot? a pH below 6 will reduce the plant's ability to uptake these elements

Measuring the pH of R/O water is somewhat dodgey, it seriously changes pH just by looking at it. I very much doubt it has any affect on soil pH though and would assume it rather changes pH instantly to its enviroment. At the moment its not suitable to measure run off as the plant just been given a watering with 0.5ml/l of biobizz grow but will get on it in a few days. Plant has also been rather severly cut back as it was really bushy. More to the point though, this plant isnt important. What important is that i dont get this issue with the 600+250W grow from clones im planning to do coming weeks.


Your idea about K-def got me thinking though..
The 'dolomite lime' i've added is, loosely translated, called garden lime. On the other hand on the back of the box there's numerous mentions of dolomite lime. Here's the relevant data, unsure if you can get anything out of it though. But if its indeed the wrong kind of lime i suppose that could explain K lockouts.

Helpfull translations:
kalk = lime
kemisk = chemical

[The Cannarchist]

How's your new growth now?