SOIL Lock out or cold problem

[stric]

Dear,
can you pleas give your opinion...
First time growing and now is 4 week in flowering.
Noticed that lower leaves start having yellow edges and become all yellow and falling down. Upper leaves are for now ok.
Ph - before watering 6.0 - run of from 6,8 - 7.2
Nutrients - Biobizz Bio Bloom 3ml/L, before in vegetative - Biobizz Biogrow around 900-1100 PPM. Nutrient and GHE Ph down were added each watering.
Today was checked runoff and PPM was really high from 2500 - 3500 ppm - I think this is a lot too much - how much is ok 1300PPM?
But how i was looking on internet this is not nutrient burn? Or my thinking is wrong?
2. Temperature in grow box is 23 degrees Celsius when lights are on and when are off may fall down to 14 degrees Celsius ( I know this is to low). Fans are working 24/7. Is better to turn off fans for time when lights are off? This wont decrease temperature so much.
Humidity is 35-40%.
What in your opinion is wrong? Do you suggest flushing or just adding pure water-and how long?
Thank you very much.

[UrbZ]

It seems your runoff is way to high pH wise 7.2 is pretty out of range.

High PPM at runoff is usually do to high levels of food left in the soil combined with washout from the medium.

Cold temps would not cause this. Just slow growth and changing color pigmentation.

Im sure you are correct in thinking you need a flush. I would suggests flushing with 5.5 pH'd water until you get to about 6.2 to 6.4 runoff.

You probably most likely do have a nute lockout

Also fans on at night are just as important as lights on.
Lights on they cool the plant. Lights off when RH is highest they circulate air to keep moisture buildup down. Especially in flower when you are trying to avoid bud rot.

[greenforce]

I was dealing with something similar going on. I was using cheaply filtered tap water. I am on a rual water system so the water is not consistant. Long story short, I started hauling in well and spring water. After the flush and first post watering the new growth started coming in with a renewed vigor and a more brilliant color. A note before I go. Before I went to well water I gave catching rain water a shot. I'm know it was better than the tap but, it came with with flying pests. I should have filtered. Well and spring water come with all those minnerials. Bonus !

[JohnC]

What I didn't see mentioned is the type of soil you are using. Can you tell us more about it? (brand, NPK, etc.)

If you're growing in a "hot" soil and then adding nutrients in your watering, that could be a factor in the problems you're seeing. In any case, it sounds like a good flush is in order.

[D.A.A.S.69]

You would think it's coco, not soil, being he's watering in at 6.0ph.

[stric]

Thank you all for replays. Soil from the beginning is Plagron Grow mix.
So you suggest flush is necessary.
Ok before flush will be made - flushing with water without nutrients and ph 5.5, and stop when runof water will be 6.3. And how much PPM (runof) should be at the end of flush?
When should start adding nutrients? Next watering or at the end of flush?
Is flush in 4 week in flowering big issue?
Thank you all

[alltatup]

stric, I always start to lower my nutes in the second half of flower.

[UrbZ]

Yup flush til you hit that pH. Dont worry about ppm runoff that will always be hinky.

It will not hurt being week 4 of flower. After the flush

completely let it dry before next feeding. Feel free to hit it with nutes after the flush on that next feeding as well.

[stric]

Thank you, all the best