Yellowing leaves (again)

[KennyDC]

Hi all. I've read everything on the site concerning yellowing of leaves, but still not sure if my problem is nitrogen deficiency, a PH that is too high, or just normal! The yellow leaves are mostly on the bottom but seem to be happening routinely, not just to the very early leaves. Some of the leaves are midway up the plants. A couple of leaves have yellowing on the tips. BTW, there have many, many more yellow leaves at the bottom, but I've pulled them off. My hunch is that the culprit is that the PH is too high, but I'd love to get your opinions.

Here are the details of the environment...

The plants are about 3 months old with a height of 18" to 28". For the last 6 weeks, they've been growing under four 100w 3K LEDs plus two Feit red-spectrum LED grow lights on a 12/12 light cycle (they're not on in the photos). The temps are mid 70's when the lights are on, and mid 60's when off (it's winter here, they're in the basement and I'm heating 24/7 with three 100w incandescent light bulbs hidden below the pots so their light is not a factor).

The PH is 7.5-8.0, which I know is high. Six weeks ago, I began adding PH down to the water, but it has yet to actually change the PH of the soil. None of the larger plants have started budding yet even though they're on the correct lights and timing cycle to do so (though a couple of the tiniest plants, oddly enough, seem to be budding).

Questions...
* What do you think is causing the leaves to yellow, or is it normal?
* Should I do my best to get the soil down from a PH of 8 to 5.5-6.0?
* If so, what concentration of PH Down is safe to add to the water without shocking them?

Thanks for any expert advice you can offer!!

[OlderNOTwiser]

I like the use of the bulbs for heat. Nice touch! How many plants do you have in these pots and how large are they? What type of grow medium? Perlite? Nutrients? Yes, you absolutely need to get the pH dialed in. The 7.5 - 8 you mention is read from where? Input or drainage?

[KennyDC]

Yeah, the three 100w bulbs seem to do the trick nicely. There are about 10 plants in the two smart pots. I'm using regular potting soil with no added nutrients. The PH of 8 is from a meter I have that reads the soil. When I use it to test the water I'm using with the added PH down, the PH level of that water is something like 4. But after doing this for weeks, the PH of soil has not moved off of 8. Thanks for your advice.

[SoOrbudgal]

Dude you have a male plant in there I see balls

[KennyDC]

Thanks. I just noticed that as well. I did kill about 4 male plants from the batch many weeks ago, but I'm pretty sure this guy didn't show up till very recently.

[Gluteous]

What are you feeding them and how often? They look hungry, which would be expected in regular potting soil.

[KennyDC]

Up until now, I haven't been giving any nutrients. I just started with Nature’s Care plant food with 7% nitrogen & 6% phosphate. Is that okay?

[dilvish]

Based on your description it seems like there are all kinds of problems. First off I may not have read or seen anyone mention it but 5 plants per pot? I'd say that's a big problem right there...why would you want to grow so many in the same pot? I personally grow one plant per 5 gallon pot. Eventually yours would become root bound. Not to mention if they are different strains they would have different requirements in terms of light, nutes etc.

The PH level of the water is high for a soil grow and therefore the plants can't absorb nutrients very well and in that case the nutrients already present in the soil may have been too high or too low to begin with. At 12 weeks, 7% nitrogen is way too much in my opinion and won't do anything for the plants at this late stage.

Additionally it sounds like you don't have a PH meter that measures water but rather you have a PH meter that measures soil. In order for your soil to come down in PH it has to be flushed with properly PH'd water. Simply adding PH down without a PH water meter is like throwing darts at a target with a blindfold.

Unfortunately at 12 weeks there is likely little you can do to save these plants...the leaves at the bottom are turning yellow likely because the plants are ready for harvest at 12 weeks (3 months). The fact that they didn't flower is a combination of everything mentioned here.

Chalk it up to a beginner grow and start again...read some or all of the tutorials on soil grows on www.growweedeasy.com and you will have a better chance at a decent yield.

Good Luck