Really Confused! PH Problem?

[Marleno]

Hey!
I have some barely vegetative plants that I'm concerned about, and I can't figure out what is wrong for the life of me! For some background, this issue started about two weeks ago when I transplanted my plants into new potting soil which is the Fox Farms brown bag. At the same time, I fed them less than half the recommended amount of Fox Farms Grow Big nutrients. Before this, they were healthy little seedlings growing fast. Now, they continue to grow, but each set of leaves becomes sickly looking after a couple days. At the time of the transplant, I did not test the PH of my nutrient solution. However, I've tested it now, and while my water runs at about a 7, the nutrient solution brings it down to about a 5.5-6. Up until now, I thought my problem might be the PH as for some reason, my soil always gives a reading of 7+, so wouldn't it make sense that the more acidic nutrient solution would work to amend that? I thought perhaps the nutrients made the plants too alkaline, but now I know that isn't true, and I'm stumped. My soil does not change in alkalinity no matter what I try. I haven't tested the run off yet, but that is my next step. Below are my theories:
1) Nutrient toxicity- Perhaps I overfed my plants since they were so little although I didn't think it displayed as a toxicity.
2) Problem with soil- Everyone and their mother recommend this soil, however, mine was very dry upon arrival and wouldn't retain water. Maybe mine is defective somehow?
3) Humidity- the humidity in my grow room is usually 50-60%. While this isn't ideal, I didn't think it could have an impact like this.

Do these pictures seem like any problems anyone has run into? I'm so confused! My next idea is to transplant them back into a soil I've used in the past and had no problems with once they are big enough.

 

[Dusted]

Looks like pH problems to me. It all depends on what the soil was buffered with. Try getting it down some more with just pH 6 water. Appears to be nutrient lockout

 

[Marleno]

Thank you for confirming it's PH problems! I thought I was going crazy and missing something for a minute there. What you said makes sense, and I'm definitely going to try that. Fingers crossed.

 

[Emilya Green]

Hi @Marleno and welcome to the forum!

It is really hard to see in that purple light, but I think I have a good idea what is going on, and how best to help you.
First, your deficiency looks to be nothing more than a common magnesium deficiency, and a little bit of calmag supplement will fill in this gap wonderfully and keep your plant from getting any worse.

Now let's tackle pH. You have a fundamental misconception as to how this all works, and I think I can clear it up for you and get you all sorted out.
First off, your very good FF soil is buffered at the top end to about 6.8 pH as are most commercial soils designed to grow pot. This means that the base pH of your soil, or the pH that it tries to revert to when dry, is 6.8 pH. This is done purposely, even though 6.8 is on the upper end of the soil pH range of 6.2-6.8 so that when you water with a fluid that is set at the lower end of the range, such as 6.3 pH, the buffers in the soil set up a positive drift in your container. When you water with a fluid adjusted to 6.3, 6.3 is the pH of your container of soil. The adjusted water overloads everything else, and that fluid's pH takes over.
As the plant uses that water, the water table level in the container begins to drop, and the soil at the top begins to dry out, and as it does, it gets closer and closer to the base pH of 6.8... drifting all through the range as it dries. This process happens continuously as the plant uses more water and the water table continues to drop, and actually you have different pH levels in different places in the container, all dependant on how wet it is.
Knowing this, all you have to do as a proper gardener is adjust every fluid that hits your soil to 6.3 pH. The soil takes it from there, and does all the magic for you. It is no harder than this. Do not try to adjust the soil by coming in low. Water at the pH that mathematically is proven to have the most nutrients the most mobile, or 6.3 Also, since the usual recommendation is to give water/nutes/water/nutes all through the grow, on the times that you give plain water, adjust your pH down to 6.3. When you add nutes, adjust you pH UP to 6.3. Get into the proper range, and I believe all of your problems will go away as long as you don't have other problems like over watering. The calmag is pretty commonly needed when people run with LED light though... and it again is going to work best at 6.3 pH.

 

[Marleno]

This is super informative and helpful, thank you. I had a general idea of how PH works, but I didn't know that, and I will definitely heed your advice. Thank you again; this will help me to be a better gardener!

 

[10gal]

Hi @Marleno and welcome to the forum!

It is really hard to see in that purple light, but I think I have a good idea what is going on, and how best to help you.
First, your deficiency looks to be nothing more than a common magnesium deficiency, and a little bit of calmag supplement will fill in this gap wonderfully and keep your plant from getting any worse.

Now let's tackle pH. You have a fundamental misconception as to how this all works, and I think I can clear it up for you and get you all sorted out.
First off, your very good FF soil is buffered at the top end to about 6.8 pH as are most commercial soils designed to grow pot. This means that the base pH of your soil, or the pH that it tries to revert to when dry, is 6.8 pH. This is done purposely, even though 6.8 is on the upper end of the soil pH range of 6.2-6.8 so that when you water with a fluid that is set at the lower end of the range, such as 6.3 pH, the buffers in the soil set up a positive drift in your container. When you water with a fluid adjusted to 6.3, 6.3 is the pH of your container of soil. The adjusted water overloads everything else, and that fluid's pH takes over.
As the plant uses that water, the water table level in the container begins to drop, and the soil at the top begins to dry out, and as it does, it gets closer and closer to the base pH of 6.8... drifting all through the range as it dries. This process happens continuously as the plant uses more water and the water table continues to drop, and actually you have different pH levels in different places in the container, all dependant on how wet it is.
Knowing this, all you have to do as a proper gardener is adjust every fluid that hits your soil to 6.3 pH. The soil takes it from there, and does all the magic for you. It is no harder than this. Do not try to adjust the soil by coming in low. Water at the pH that mathematically is proven to have the most nutrients the most mobile, or 6.3 Also, since the usually recommendation is to give water/nutes/water/nutes all through the grow, on the times that you give plain water, adjust your pH down to 6.3. When you add nutes, adjust you pH UP to 6.3. Get into the proper range, and I believe all of your problems will go away as long as you don't have other problems like over watering. The calmag is pretty commonly needed when people run with LED light though... and it again is going to work best at 6.3 pH.

is that just for soil or does peat mixes do the same?
I feel like ive noticed something similar

 

[Emilya Green]

is that just for soil of does peat mixes do the same?
I feel like ive noticed something similar

peat is in the other end of the spectrum... it is a soilless mix and since it doesn't interact with the fluids like soil does, it does not saturate with water, it simply exists in the water, it is basically a hydro system. Your range there is 5.5-6.1, but here is the funny thing... the pH of the water is still important, but as the nutes in the water as well as the water get used up... the pH begins to drift just like in soil. The water is 7.0 ph and nutes are acidic, and as the mixed in nutes in the reservoir start getting used up, the water's pH starts taking dominance over the pH of the mix. The less nutes left in the mix, the more base the solution becomes, giving you a positive drift. This is why it is recommended in a hydro system to come in at 5.5-5.8, and then let the drift take it up through the range all the way to 6.1.

 

[10gal]

peat is in the other end of the spectrum... it is a soilless mix and since it doesn't interact with the fluids like soil does, it does not saturate with water, it simply exists in the water, it is basically a hydro system. Your range there is 5.5-6.1, but here is the funny thing... the pH of the water is still important, but as the nutes in the water as well as the water get used up... the pH begins to drift just like in soil. The water is 7.0 ph and nutes are acidic, and as the mixed in nutes in the reservoir start getting used up, the water's pH starts taking dominance over the pH of the mix. The less nutes left in the mix, the more base the solution becomes, giving you a positive drift. This is why it is recommended in a hydro system to come in at 5.5-5.8, and then let the drift take it up through the range all the way to 6.1.

interesting
thank you