Problem with plants, visible through necrosis in thier leaves

Hi there fellow growers! This is my 9th indoor grow and for the first time I am facing a problem I cant solve. I have four F1 females in four different pots with the same compost. (The same I have been using since my first grow).
After 20 days in VEG, the leaves started turning yellow. The next stage started with the leaves turning brown, which later translated into necrosis; the leaves twisting and drying around the brown spots. This can be seen clearly in the photo.

I want to highlight the fact that I have always grown my MJ in the same grow room, using the same compost for soil. This is why I am so bewildered, as I cannot solve this issue.
Initially, I got the feeling the plant was lacking nitrogen (As the leaves turning yellow around the edges usually mean that). I applied the usual fertilizer for nutrients in VEG. It seems like the process has been hindered but goes on. It may be that they are lacking nitrogen, but there MUST be something else wrong. From my research on the internet, I understand this is probably a defficiency. However, I fear there may be a fungus infection or something else.

I know from my personal experience that here at rollitup there are plenty of experts who can help.
Please do so.

I hope the pictures are useful.

That doesn't look like a nitrogen issue to me. When plants are getting N deficient the lower leaves turn a pale green, eventually fading to yellow as the leaves become soft and fall off. Typically there are not any necrotic patches on the affected leaves, they just go pale and drop and this progresses up the plant.

Are you growing in straight compost?? Or do you mean a compost-based potting mix? And by the same you mean that same brand or that you're re-using mix from the previous grows?

Is there lime in the potting mix and can pH issues be ruled out? How much of the plant is affected and which part(s)?

Some of these may help you determine if it is a deficiency and what is lacking: http://www.greenmanspage.com/guides/plant_abuse.html
http://www.icmag.com/ic/showthread.php?t=11688

I believe there is a similar guide on here as well.

Pictures of leaves are almost never terribly helpful, but pics of the whole plant are usually more so...that way we can see where it is yellowing, and what else might be happening...I find most issues are over nute related more so than needing nutes... and pH can cause anything to happen...

When you say that you have been using the same soil, do you mean you are reusing it each time, or you keep getting the same stuff...?

I reuse my soil, but only 4 or 5 times...I add a few amendments each time, but it seems some things get built up in the soil, while others get totally depleted by the 4th or 5th time and I start to see weird leaves...

Hi there! I meant to say I use the same kind of potting mix. I buy my supplies at a local grow shop; its organic and has never failed. so yes, "compost-based potting mix". I do not re use the soil.
Here are some pix of the girls. The first two big plants are showing twisted leaves at the top of the plant. The one in the back on the left is actually the first one to ever show these symptoms.
Some leaves are showing necrosis I guess... but the new stems do not seem to have a problem. The problem is with the twisted leaves which are curled.
The problem is not visible in the whole of the plant, just on the middle leaves. I have looked for gnats or other bugs but nothing... hope someone´s been thru this!
Oh I would like to add that it is WINTER here.. with temperatures below 0° C (water freezing point). What I am doing is keepin the lights on during the coldest hours so the temperature inside the closet stays round 26 and 29°C.
Thanks a ton!

in addition to supplementing the nitrogen, i would check PH to make sure that's not blocking N,

then i would give it a bit of cal/mag (epsom salts), and if you can get a supplement like super-thrive or K-L-N

they provide heavy metals like mercury, cadmium and arsenic, and b vitamins and stuff. stuff people don't normally think of but are important

after that, i bet your plant does better

The plants have been in VEG for 40 days and just recently they've started showing these symptoms. Just as I transplanted from 3 L to 15 L pots. In these 15 L pots, they should be starting flowering. So, the percentage of worm humus, which is high in nitro, is very low (around 10%). This is why I rule out an over feeding of N. Nonetheless, I applied a bit of fertilizer for VEG just in case the plants needed more. I believe it is more likely to be a defficiency of N rather than an over feeding.
The varities I have this time are

2 Skunk Sensi Seeds. one presents these problems the other seems fine

1 Sweet Thai - Sweet Seeds. The one with bigger leaves on the pictures, doesnt have necrosis, just a slight yellowing in the edge of the leaves.

1 Sweet Afghani Delicios - Sweet Seeds. Necrosis on the three older leaves so far.


I have grown all these varieties in the winter before and had had great results and yield with the same HPS and growing conditions.

Although the pot is extremely wet after watering it, the plant seems to be dry. It looks sort of fallen... as if it were going through a draught.

I watered them two days ago. The temperature outside the grow room has not reached 10 ° C. The soil takes a long time to dry up, unlike in the summer. I am afraid if I continue to water them the roots may rot. I dont want to spoil the roots basically...
I do appreciate your feedback...

i really think you should rule out PH issues

ph water or soil??