This happened a few hours after using grow booster,what is it?

6.5 is the pH of what? You didn’t say anything about how long between feeding, it seems almost as if you are way over feeding it, but you gave no time schedule.

What videos?

Yes, you need to learn how to measure the run-off, it isn’t that hard, you just measure the run-off that comes out the bottom of the container. You should get a TDS meter pen, as well as a way to measure pH like strips, drops, or also a digital pH pen.

Also, are you over watering?

Fresh air 24/7? How does this work, where is the “fresh air” coming from?


Check out Robert’s video on you tube and his blog from this site

Robert’s youtube on testing soil:

Robert’s blog on testing soil:


And have you seen this:

Tip of the leave curve up

Wow, it’s amazing, I got lucky and found a video that covers exactly what you asked about testing the run-off, and then he talks about heat.

Check it out:

Then some other guy talking about just testing pH in the run-off as well. I agree, pH in the run-off can be a little lower than what you put in without it being a problem, but it is best not to let it it get too far out of range.


Thanks Mac great info.

i have my grow tent inside a room which has a small window right behind an opening that the grow tent has,i keep the window open during the day and keep it closed only for the 6 hour dark period.
i have 2 circulation fans inside the tent and a carbon filter.
i water one time with nutrients and then 2 times without.
i checked the videos you posted but i have a small problem.i water each plant with 1l of water but there is no water running off the container (there are 4 holes in the bottom of every container).should i use more water than 1l?maybe i am overwatering as mac G said but i am sure that i wait until the soil is almost completely dry before i put some water in
i also have ph and tds meters.
i am thinking of bying this
and i would like your opinion,if it is going to help or measures even how dry the container is and if the plant needs watering or not.

Yes, you need to water until some comes out the bottom. Watering should normally be done this way, to full saturation – the entire container, and then don’t water again until totally dried out.

I hear a lot of people just not seem to be happy with soil probes accuracy, I’d trust measuring the run-off more, also that meter will only show pH, moisture, temp and light. And what you really need to know is soil fertility, or nutrient concentration building up in your soil, and this meter doesn’t check for that. Learn to test the run-off, it isn’t that difficult and it sounds like you already have the tools.

Check out this link here where I go into a lot of detail about testing the run-off and watering to saturation and not watering again until very light and almost totally dried out:
Yellow spots on a few leaves of one plant, one leaf on other, none on third - deficiency?


i tested the run-off to 5 of my plants and the results are:
container 1) 6.6 ph – 1910 ppm
container 2) 7.1 – 1840
container 3) 6.9 – 1300
container 4) 6.7 – 1480
container 5) 6.7 – 1440

I’m guessing the ones with the highest run-off ppm or pH farthest from 6.5 are the ones with the damaged leaves?

actually those 5 are the least damaged,i will test the other 5 tomorrow morning and let you know.
what should i do if ph or ppm are too high?
i checked the video you posted and this guy says that the ph of the run-off to all of his plants is about 5.5 and ppm should be 1800 the most if i understood correctly.

I don’t think your soil is mostly coco coir, and so it should be more at 6.5pH for soil, 5.8 for hydro.

Normally with many nutrient lines a ppm of 1800 in the 0.70 conversion is ok, it is an EC of 2.5 to 2.6 and is what he is probably talking about. The 0.5 PPM conversion would only be about 1250.

However, a PPM of 1800 in the 0.5 conversion would be like 3.4 EC, and would be too high with most nutrient systems.


so you re saying that ppm in my containers is too high?i really have a problem understanding all the things you said above so please forgive my stupidity for asking again.
and if they are too high what should i do?
and still haven t figured out the reason why my plants are still too short and what to do to fix this.they will be 2 months old at 11 of november and the tallest of them all is 48 cm,but most of my plants are around 30-40cm.
if you could please give me some advise of how to fix this with simple words i would really appreciate it,
i am a guy who has started to love growing weed but i have never planted anything before,so my knowledge about growing plants in general is extremely poor

Yes, very likely it is too high, both pH and PPM.

and what does it need to be done to fix this?
is this the reason for their slow growth?

It is very likely part, if not the main cause of your problems.

You need to bring the pH to 6.5, and probably flush, or only water with pH adjusted water to get the ppms down.

so i stop nutrients until i get the ppms at what numbers?
and how will i lower the ph?i am watering with 6.5 should i water with a lower ph to something like 6.0?

You might need to flush your soil in the ones that have the worst problems and worst ppms and/or pH.

You would flush with low or zero ppm water to lower your ppms, ppm and pH recommendations are in the nutrient schedule.

Yes, you would need to water with a lower pH to adjust your pH down. I went into detail about how to understand your pH readout numbers in the link above I gave you. Keep in mind his numbers are for coco, you have soil, as I said your pH should be at 6.5


ok i ll do that thank you very much

i can t find the nutrient schedule but i read that ppm should be around 1200 at this phase of growth(correct me if i am wrong).the thing is that my tap water is at 1500 ppm and is not going to rain anytime soon here so i can t ‘‘steal’’ some rain water from nature.
so what other solution is there?
now about flushing since i haven t done it before…what i did was to use a lot of water in every container until the tray was completely full but i did not throw away this water,i just left it there and i think that this was probably a mistake?
i also got rid of all yellow and damaged leaves in every plant and i don t know if this was right

i checked the run off at one of my plants today and results are not good,ph was at 6.9 last time i tested it now it s 6.7 and ppm raised from 1300 to 1500.
i lowered the ph to 6.0 from 6.5 as you told me but there is no difference,it was 47cm last week and it only got taller 2 cm in 7 days,actually i see more fan leaves changing color every day and simply die after a few days.don t know what else to do so please if there is nothing more i can do to save them tell me so i will stop right now and buy some new seeds and start all over.
i just haven t figured out what caused all this so i won t do it again,all i know is that problems started when i begun to use robert’s nutrients

You still haven’t told us what you were doing with the nutrient system. You never told us your feeding regiment. Were you adding booster to every single watering?

A PPM of 1500!!!

The pH issues are probably because of the water you have been using, any nutrient or soil is going to have problems if you use hard water. Water with a PPM much above 50 PPM (0.1EC) can cause problems in the long run even with the best of nutrients. You can maybe make up to 150 ppm (0.3EC) water work, but you have to be really careful of alkali salt build up in your soil (same thing as lime scale in your plumbing or on your faucet fixtures) and nutrient lockouts and toxicities as a result of said build ups with water this hard or harder.

I’ll tag @latewood to this conversation as he’s used the booster. He might see something I missed, and he works in soil more often than I do.