Help! What should I do?

[jdesmedt]

This is my first posting here so please don't be too rough on me. I feel I've hit a wall and badly need some input...

I'm in week 2 of flowering this 50/50 indica/sativa strain in coco/perlite mix.

Leaves started showing signs of what appeared to be calmag deficiency. This would make sense as I did provide calmag but it was the end of an old bottle and I just read somewhere that calmag goes bad after a while ? This is my first grow in coco and I perhaps made the mistake of not watering frequently enough, which could account for the calmag deficiency. In any case, leaves started showing fading between veins. I didn't react quickly enough and now I've got some pretty sick-looking girls (see pics). I belatedly changed to a fresh calmag bottle and upped the intake (root + foliar) but I guess there's no turning back. The girls are damaged, period.

My question is as such: should I keep going or trash them now and start over? Obviously, I don't want to wait another 6+ weeks to harvest if the outcome (yield/potency) is going to be disappointing. Electricity is expensive enough as it is where I live, don't want to be spending it on a dead end.

What do you think?

 

[jdesmedt]

Thank you Cyruscrops for your prompt reply and offer for help.

Although I agree with you it could be light burn, I'm guessing I might be dealing with multiple problems at the same time, including calcium deficiency as seems to be the case from the brown spots on the leaves (see attached pic). Light burn does not produce brown spots like this. And lower leaves are also curling downwards, although they're away from light.

Btw the plants were fine until I switched them to 12/12 and moved on to a different NPK mix.

Let me try and be a bit more complete:

LIGHT
600w led quantum board Samsung LM301H, distance to plant: 40-50 cm at full blast on 12/12 schedule.

NUTRIENTS
Grow: calmag (residue of old bottle, probably no longer good) @ 300ppm, NPK @ 50-24-26%, root growth stimulator, humid acid, ph between 5.5 and 6.5 and final solution below 1500ppm -> no problem so far

Bloom: calmag (residue of old bottle, probably no longer good) @ 300ppm, NPK @ 29-35-35%, root growth stimulator, humid acid, ph between 5.5 and 6.5 and final solution below 1400ppm -> after 10 days first signs of stress appeared.

I should say I also added Oligomix after 12/12 switch (mix of zinc, bore, copper, molybdenum, manganese) as my NPK mix does not contain oligo-elements.

I use rain water. I measure runoff: ph6.2 and 1400 ppm.

WATERING
From cuttings: due to large pot (6L) I only watered when medium (coco/perlite) dry to encourage root growth - so once a week. Plants were doing fine. Then later moved to once a day with lots of runoff. In final stages of grow, watering twice a day.



All this seems ok to me no? I might have some light burn - possibly - but light burn cannot be responsible for all of it surely.

Anything I can think of is calmag deficiency which would fit my using old calmag and not watering enough?