Yellowing in early flower after flush and synthetic nute switch

The typical issue is pH trending lower during a grow due to salt buildup. I’ve never encountered pH trending higher. You can treat it with a flush or a product called pH down, but that won’t address whatever the source of the problem might be.

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When I check my PPM its almost identical to the Chart I use. I can switch one of my TDS from PPM to EC. Which my chart also covers EC. The other doesn’t.

That’s weird then, I’ll have to Google around and see what might be causing it as both plants drifted higher from 6.5 to about 7.1 during the slurry test…

Found this online:

“Quick absorption of Nitrogen can also cause the pH of your substrate to rise. If the pH rise is due to absorption, increasing Potassium (Bloom) can help in lowering the pH of the root zone.”

As we established above, I was only using Tiger Bloom and should have been using that with Big Bloom (which is arriving today) so maybe that’s what is happening? Low potassium?

You shouldn’t have low potassium if you have been feeding Tiger Bloom. The FF Trio is meant to be all used together for a healthy plant. Big Bloom can be particularly important because it provides the micronutrients (copper, boron, iron,…) that cannabis needs.

I’ve never heard of any nitrogen product that raises pH. The Fox Farm Trio is salt based and drives lower pH over time. Did you put a lot of lime in your soil?

I got my soil from A Pot for Pot as an all-in-one type of pack, I’m not sure what the issue is then but I’m going to flush the soil again and give a proper feeding with tiger bloom and big bloom - checking the Ppm as per the charts above and see how that goes.

What’s your water source? Tap? Like what water do you use to normally water?

Use sledgehammer and flush the heck out of it.
Put it in the bathtub or the sink and just let water run through it for like… 30min
Then your know you flushed.

Next get your good water and add a full feed, if you got your tds meter off amazon it’s probably a 500 scale most are @MrPeat idk where or what one you got lol.
Once you have a 5 gallon bucket full of feed, PH that bucket (can’t Remeber if pot for pot is coco or soil if it’s coco PH to 5.8,if it’s soil 6.5)
Now pour that whole bucket through your pot while still in the sink or bathtub.

Boom you did a fill flush and feed. That’s how it’s done, the feed will PH the soil because it holds a charge anything with less than 200-300 ppm doesn’t hold a PH and the stronger the ppm the better it holds it.

Do this all In one sitting. Over watering a plant is when you keep. The roots wet for multiple days, flushing it like this won’t over wster it.

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Thank you so much for this, luckily I did exactly as you instructed last night, flushed and let it drain out with sledgehammer then did a full nutrient feeding, the leaves have perked up in response to the watering but will keep an eye of the yellowing over the next few days.

Can I ask though as per the feeding chart, the dosages stay the same like 3 Tsp big bloom, 2 tiger bloom in week 6 at 1250 Ppm and then in week 8 it has the same nutrient dosage but a lower Ppm range to 700, how do I use that same nutrient dosage and hit those different Ppm ranges?

Follow the ppm rating, just be mindful of the ratios
Your welcome
:smile_cat:

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So just a little update for everyone, I did the flush and the nutrient feeding as per the 500 scale for Ppm’s and pH’d to 6.6, checking the Ppm after adding the nutrients before feeding as well.

I removed some of the yellow leaves so that I could keep an eye on the yellowing and I’m not sure if it’s still spreading just yet but some of the top leaves has developed a purple colour at the tips? Any idea what that might be?



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@MidwestGuy @MrPeat

The purple could be genetics.

OVER/UNDER-FERTILISATION. A lack of key nutrients will cause cannabis leaves to turn yellow and wilt. … As a key macronutrient for cannabis plants, nitrogen deficiency or burn usually causes these symptoms. Nitrogen deficiency starts by yellowing the edges of leaves before working its way inwards

These leaves will never recover. If you address the problem new leaves will turn green.

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Yellowing is lack of nutrients or PH lockout. But the damage has been done and can’t be fixed only stopped from getting worse.

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The other plant from the same seed has some purple leaves by the buds so makes sense.

@Nicky I’m keeping an eye on the yellowing but removed the worst ones so I can tell if it’s continuing

Thanks again

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Plants are very different from seed to seed, that’s why Commerical. Operations find the plant they want after dropping let’s say 100+ seeds, clone the best plant and then keep it and just run clones.

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It’s not going well so far it seems, just gave a water feeding but the yellowing keeps spreading… Can’t figure this one out.




I had done the flush until the Ppms hit about 400 and properly fed with the nutrient ratio whilst following the guide about the Ppm as per the week of flowering and pH’d it properly, I’m struggling to think that this is under fertilisation like @MrPeat mentioned before - maybe the flush didn’t work but at this point doesn’t it seem like nitrogen burn?

I am at a loss. Yellow leaves can be caused by not getting enough water. You have to remember as the plants gets bigger, you need to use more.

I never have issues like this.

@Myfriendis410 Can you help please?

What’s your run off ppm and run in ppm?
What nutrient are you using and what weeknof flower are you in.

I usually water at least a gallon but more if there isn’t 30% runoff, in my research I came across this:

I fed the nutes immediately after doing the flush and didn’t let it dry, do you think this might have merit?

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Sounds possible I’m not familiar with the product.
I would re flush just with water and full feed
Because its already dried once since then right?