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Really need a couple of diagnosis’

DTOM420

Member
I need some help diagnosing 2 problems. The first is two 17 day old CBD auto strain seedlings. They’re in 5 gallon grow bags in a soil mixture but germinated in a 16oz cup size patch of 50/50 promix and perlite. They started out looking great but have yellowed considerably in the last few days. They’re under a 600w (at the wall) 3000kLED fixture that’s 3.5’ above them eand they’re slightly shaded by some bigger plants in flower. They have been getting distilled water since I put them in cups to pop. Temps range from 78°f-72° w/ RH of 55%-60%. The soil tests in at a pH of 6.8. I’ve been feeding them with distilled water until now but I decided today to start giving them some light nutes because of the yellowing. So, I pH’d our well water to 6.5 and gave them some 1/4 strength of a local organic liquid nite that’s 6-12-6 and has a soil activator. I’m surprised that there’s any deficiency going on but I’m concerned about the yellowing. My first suspect is nitrogen but I can’t imagine and next would be phosphorous but I added 5 tablespoons of seabird guano to the mix so there ought to be plenty of phosphorous. I’m at a loss. Sure could use some advice here.

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This next plant has been a struggle. It’s a 75 day old Blue Widow in 7 gallons of soil. I revenged her after sexing her and she’s gotten out-of-hand dense without the stretch I would have liked. The issue, as you can see is interveinal yellowing that starts on the leaf edges includes new AND older growth. After this first arose, about a month ago, I discovered that the pH had dropped through the floor (I never could figure out exactly why) down to around 4.2! So, I attributed the yellowing at that low pH to a Magnesium deficiency due to pH lockout. I sprayed her with water and epsom salt, flushed her with Sledgehammer and un-pH’d well water that was around 7.7 and continued to water with that high pH water She slowly started to respond and greened up some; but now the same issue has returned and I can’t really blame pH, I don’t think. The soil tested at 6.5 a couple of days ago (following 2.5 weeks of watering with slightly alkaline water) and the last few waterings have been pH’d to 6.6

Excuse the water droplets on the leaves in the pics. I busted her heavily with epsom salt water and THEN thought to take a picture. Lol! FWIW, the 3000k bulb makes the leaves look even more yellow in these pictures than they look in reality

picture.php
 

Lester Beans

Frequent Flyer
Veteran
Both plants suffer from pH flux and starvation. I would feed them both half strength of that 6.12.6 and make sure to carefully pH to 6.5-6.8. I would not give them any water not pH proper, even if it doesn't contain nutrients. The leaf twist is a good sign to look for when pH is off.

If this does not work, I would get an RO filter or store bought spring water.

Good luck, let us know how they respond
 

buzzmobile

Well-known member
Veteran
17 day old seedlings in a 5 gal. grow bag can be a problem controlling moisture. It's easy to over water. Yellowing leaves can be a sign of too much water.
 

DTOM420

Member
Both plants suffer from pH flux and starvation. I would feed them both half strength of that 6.12.6 and make sure to carefully pH to 6.5-6.8. I would not give them any water not pH proper, even if it doesn't contain nutrients. The leaf twist is a good sign to look for when pH is off.

If this does not work, I would get an RO filter or store bought spring water.

Good luck, let us know how they respond

Are you referring to the two seedling plants? Or are you referring to the 2 seedlings AND the adult photo plant as having the same problem?
 

MJPassion

Observer
ICMag Donor
Veteran
Seedlings look like they're beginning to suffer from a pH imbalance. Due to the yellowing at the tops of the plants, you are dealing with an immobile nutrient issue. If they were lacking N (a mobile nute) the yellowing would start on the bottom and progress toward the top.

If you don't already have one, get a soil pH probe and test the soil.

It would also be wise to get your water tested to see what's coming from your well.
If it's high in some minerals you might need to adjust your feed rates.

As far as the lower plant pic, check pH first and adjust if it's off.
Otherwise it looks like a Mg issue to me as well. To test you can mix 1/4tsp (1.2g) Epsom salt to a quart (liter) of water and give your gals a foliar spray. If the yellowing begins to go green you know your not getting adequate Mg into the plant.
 

TanzanianMagic

Well-known member
Veteran
I need some help diagnosing 2 problems. The first is two 17 day old CBD auto strain seedlings. They’re in 5 gallon grow bags in a soil mixture but germinated in a 16oz cup size patch of 50/50 promix and perlite. They started out looking great but have yellowed considerably in the last few days. They’re under a 600w (at the wall) 3000kLED fixture that’s 3.5’ above them eand they’re slightly shaded by some bigger plants in flower. They have been getting distilled water since I put them in cups to pop. Temps range from 78°f-72° w/ RH of 55%-60%. The soil tests in at a pH of 6.8. I’ve been feeding them with distilled water until now but I decided today to start giving them some light nutes because of the yellowing. So, I pH’d our well water to 6.5 and gave them some 1/4 strength of a local organic liquid nite that’s 6-12-6 and has a soil activator. I’m surprised that there’s any deficiency going on but I’m concerned about the yellowing. My first suspect is nitrogen but I can’t imagine and next would be phosphorous but I added 5 tablespoons of seabird guano to the mix so there ought to be plenty of phosphorous. I’m at a loss. Sure could use some advice here.

View Image

View Image


This next plant has been a struggle. It’s a 75 day old Blue Widow in 7 gallons of soil. I revenged her after sexing her and she’s gotten out-of-hand dense without the stretch I would have liked. The issue, as you can see is interveinal yellowing that starts on the leaf edges includes new AND older growth. After this first arose, about a month ago, I discovered that the pH had dropped through the floor (I never could figure out exactly why) down to around 4.2! So, I attributed the yellowing at that low pH to a Magnesium deficiency due to pH lockout. I sprayed her with water and epsom salt, flushed her with Sledgehammer and un-pH’d well water that was around 7.7 and continued to water with that high pH water She slowly started to respond and greened up some; but now the same issue has returned and I can’t really blame pH, I don’t think. The soil tested at 6.5 a couple of days ago (following 2.5 weeks of watering with slightly alkaline water) and the last few waterings have been pH’d to 6.6

Excuse the water droplets on the leaves in the pics. I busted her heavily with epsom salt water and THEN thought to take a picture. Lol! FWIW, the 3000k bulb makes the leaves look even more yellow in these pictures than they look in reality

View Image
What has happened is that you had way too little magnesium to begin with because of the distilled water, and now the plants have hit early flowering, and need more magnesium, and phosphorus for the root expansion that is synonymous with flowering.

The latest pictures look like potassium deficiency.

What I would do is this.

1. Forget all the other advice, you need to do one thing only.

2. Forget about ph-ing your water.

Most important:

3. Give the plant 1 full high dose of a balanced nutrient (5-5-5, 10-10-10), and then only bottom water with your well water, until any nutrient deficiencies show. Only feed from the top, and rehydrate the plant from the bottom.

This will give the plant time to get adjust to the new nutrient level, and encourage the roots to search for more nutrients in the medium. It also creates a lot of stability in the medium, because nutrients aren't continuously washed out of the medium. Plants like stability.

Why?

Promix is a light mix, that does not have a lot of nutrients in it to begin with. Add 50% perlite, and you reduce the nutrients even more. Also, perlite has a pH of 7.0 and light mixes usually have a pH of 6.4. It is ideal for mixing into a supersoil with bloodmeal, bonemeal, etc.

pH in organics vs hydro or coco

I would aim for a pH of about 7 if you go for an organic grow. Which will happen automatically when you mix nutrients with water that is 8.0 pH or so.

In organics, pH is about making microbes happy. In hydro and non-organic coco, it is about the range at which naked roots best absorb mineral nutrients. Usually that's between 5.8 and 6.4 max. Microbes have a large range from 6.5 to 7.5. So keeping things around 7.0 by selecting your water, nutrients and medium (not pH-ing with acid) gives very trouble free, work free results.
 

Creeperpark

Well-known member
Mentor
Veteran
Wow

Wow

Tanzanianagic, you are right on! Super advice and well written too. I learn a lot from your threads bro. Thanks!
 
7

707OGBUSH970

That definitely looks like textbook magnesium deficiency. This Tanzanian guy definitely has it right. Good advice.
 

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