Lime green leaves on top with brown spots on lower leaves

[Mark1986]

I’m new to growing in a tent and apologies if this is discussed in other threads. I’m seeing a lightening of the green on the leaves with brown spots appearing on the lower leaves. My research suggest a potassium deficiency possibly brought on by too high soil ph.

The condition of the grow is 66-71 Fahrenheit at about 55-65% humidity and is approximately 5 weeks into the grow. Feed a diluted feed about every 5 days (but only in smallish amounts as needed). Lights at 70% led panel set about 2 feet above. Growing in a mix of about one third soil, one third compost and one third perlite with rocks in the base for improved drainage.

I have a second plant next to it growing very healthy and no issues. One is White Widow and the other is Alaskan Thunderfuck - unfortunately I lost track of which is which.

Love anyone’s thoughts or advice so I get it on track with other. First two photos are the one that’s struggling. Last photo is the healthy one.

 

[Vegguerilla]

New growth forming seems to be OK fella...personally I wouldn't mix soil and compost in a pot base for seedling growth as invariably balance pH is differing in both.try to stay with one media and grow rocks/perlite if possible..water pH in the range of 6.5 -6.7 is where you need to be aiming for..and make sure all water given to plant is aerated and matured a while before watering..I wouldn't feed anything just yet and any watering done just use plain....the new growth on top is encouraging and it shows that whatever the plant went through in defiency is now showing new growth to suggest its happy..some seeds take to mix soils..some don't...but seedlings are delicate and all individual..it seems OK at the moment but watch intently on that new growth...

 

[BillyBanchan]

You said, "Lights at 70% led panel set about 2 feet above."

Seems like too much light... Which light panel are you running? Also looks like Mg and maybe even Ca deficiency.

VPD seems ok, but the upper end of your humidity range at 70° results in farly low transpiration. Leaf temperature would help with knowing VPD.

Would like to know your feed EC or ppm, feed pH, runoff pH, and light specs.

Also, what's your water source? Tap, well, spring?

B²

 

[Captspaulding]

How would you like you plants sir? Well done I assume?

 

[Harpua88]

5 weeks old? And no the 3rd one isn't in any better a situation.

What's the soil like, what kind of light are we talking about? Why are you feeding at all, and have you taken a Ph reading of the soil?

When I ask what the soil is like, I mean where did you get the soil from? The ground? A bag? And the compost......your own......?

 

[Captspaulding]

5 weeks old? And no the 3rd one isn't in any better a situation.

What's the soil like, what kind of light are we talking about? Why are you feeding at all, and have you taken a Ph reading of the soil?

When I ask what the soil is like, I mean where did you get the soil from? The ground? A bag? And the compost......your own......?

Looks like fox farm m nowadays

 

[Harpua88]

Looks like fox farm m nowadays

It would almost have to be. I don't know how they cornered the soil market, it's almost like no other soil ever gets used.

 

[Captspaulding]

I stay away from the stuff, but it works for some people.

 

[Harpua88]

I stay away from the stuff, but it works for some people.

It's soil. I doubt they do something so special, so unique..........

Marketing

 

[Captspaulding]

It's soil. I doubt the do sonething so special, so unique..........

Marketing

I was just having a convo about fox farms nutrient schedule, now I do use their nutrients, selectively. But, the schedule they have out for soil, coupled with the instructions on the bottles are fully inadequate. My problem with their schedule is they want you to use a lot of it, so you go through it quicker and by more, but when new growers get caught up with issues, and they swear by that feeding schedule, it causes them to start second guessing every other aspect of their grow rig, tent/room size, lights temp and rh. It makes novice folks head spin. It couldn’t possibly be the nutes I’m following the rules ect. They should change it. It’s almost like their a big corporation or something

 

[Harpua88]

I was just having a convo about fox farms nutrient schedule, now I do use their nutrients, selectively. But, the schedule they have out for soil, coupled with the instructions on the bottles are fully inadequate. My problem with their schedule is they want you to use a lot of it, so you go through it quicker and by more, but when new growers get caught up with issues, and they swear by that feeding schedule, it causes them to start second guessing every other aspect of their grow rig, tent/room size, lights temp and rh. It makes novice folks head spin. It couldn’t possibly be the nutes I’m following the rules ect. They should change it. It’s almost like their a big corporation or something

Great, now you preserved my typos for all eternity......argh I hate typos!

Yeah and it's really fundamental/psychology. It's why a lot of people have overweight pets. We are conditioned to water, feed, give, more, add, push........ýou want to grow a plant? They like a, b, c......you want a big, healthy plant? Give them more! Plants like water, so I'm gonna give extra water! Food is good, it makes things grow, here.....eat!! I want fluffy to love me, here fluffy, have all the human food you want......

Most every product is good, but only properly applied, which usually means the amount necessary for the plant to thrive, and no more. Whatever one uses, once we get that......just like with watering, it sticks.

I'm sure Fox farms has good, rich soils and nutrients, people just need to know how to apply them.

 

[Mark1986]

You said, "Lights at 70% led panel set about 2 feet above."

Seems like too much light... Which light panel are you running? Also looks like Mg and maybe even Ca deficiency.

VPD seems ok, but the upper end of your humidity range at 70° results in farly low transpiration. Leaf temperature would help with knowing VPD.

Would like to know your feed EC or ppm, feed pH, runoff pH, and light specs.

Also, what's your water source? Tap, well, spring?

B²

Cheers for the reply…some of this information I’m still figuring out. Not sure of the VPD, I have spider farmer led light panels, specifically SF-2000. Ph is 7, not 100% sure the best way to lower the Ph and being cautious as I don’t want to “over love” my plants. Humidity tends to hang around 55-60%. Made a mistake on the lights, they are closer to 60% output at the moment. Water source is from the tap but I’ve been letting it in sit for a day before using it.

 

[Mark1986]

5 weeks old? And no the 3rd one isn't in any better a situation.

What's the soil like, what kind of light are we talking about? Why are you feeding at all, and have you taken a Ph reading of the soil?

When I ask what the soil is like, I mean where did you get the soil from? The ground? A bag? And the compost......your own......?

It’s a mix of soil, perlite and compost, it’s my own compst matured for about 6-9 months. I’ve had pretty good success outdoors in the past and have grown outdoor plants to about 10-12 foot sativas in this mix. PH of the soil is 7.

The lights are spider farmer SF2000. I’ll cut the feeding but was feeding at less than 1/2 strength.

 

[BillyBanchan]

To check VPD, you need at least canopy temperature and humidity (assuming leaf temps are 4° lower), and knowing exact leaf temps would be much better (laser thermometer).

Here's an interactive VPD chart to use. Someone here suggested it (I forgot who ): Interactive VPD Chart

As for light intensity, your light's par map will help you set the correct height and these numbers can help you calibrate a great app to measure light: Photone App

Finally, pH in your soil is something I'll let someone more knowledgeable comment on.

B²

 

[BillyBanchan]

And, fwiw, mine looked like that at exactly that stage. I decreased the light intensity, and cut my feed EC by 40%. They turned around in a matter of days.

Possibly high light levels causing higher demand for calcium and magnesium... And/or soil and water pH locking some nutrients out... Pretty sure that was my issue.

B²

 

[Harpua88]

It’s a mix of soil, perlite and compost, it’s my own compst matured for about 6-9 months. I’ve had pretty good success outdoors in the past and have grown outdoor plants to about 10-12 foot sativas in this mix. PH of the soil is 7.

The lights are spider farmer SF2000. I’ll cut the feeding but was feeding at less than 1/2 strength.

It could be something with the soil, that is very slow growth for 5 weeks. Provided your watering is on.....are you watering thoroughly? If you give them a nice thorough plain watering with no improvement, (and your light might be too close/too much power, so I would rraise that up/ lower the power)...if these things show no improvement, it could be your soil. I don't have a lot of experience making compost, I've done some, but I know it's more involved than just letting a heap.of stuff break down. It can come out with problems. if your soil is good, and already rich, even half strength feeding.......half strength for seedlings? Could still be a little toxic?

Unless there's some blind spot I think your answers are in dialing one or more of these things.

And I'm not saying you don't know about all of this, it's just about trying to flush out the answers/solutions. I'd be interested in how this ends up....