Leaves blacking/yellowing with green veins, can't seem to figure it out myself

[Y20S]

Hello everybody, here are the pictures, maybe it would help to figure it out.
FIY these three leaves were taken out of separate plants, it might be that I've overwatered one of them (the black one) but the others remain a mystery to me.
pH - just a bit over 6.5
temps get high in the summer, never over 30C though.
I'm feeding them organic compost, spray with amino acids once in a while, they seemed to like it, but the deficiency is ruining everything!
(These leaves are taken from the bottom part of the plant, and i've noticed a bit of stem purpling)

 

[coconutcurry]

I guess your plants are in flower. Which day since 12/12? How big are the pots and the plants?

 

[Douglas.Curtis]

They're starving for magnesium. Use a half gram per gallon of a quality magnesium sulfate. (epsom salt) The plants will appreciate the mag and also use the sulfur for terpene production.

 

[Budley Doright]

Nope not magnesium...potassium......

It could be both...... but the burnt margins point to potassium

 

[paradoxlost]

It's mg and k. Get a soil tray

 

[redlaser]

Could be more than one issue, but it looks like classic K deficiency, and it usually shows up where you found it in older, lower leaves.

 

[Douglas.Curtis]

I have to admit, I'm limited in diagnostic abilities. It does look slightly different than a classic mag deficiency.

I've been using Lucas formula variants for 15 years and Mag is the only deficiency I've had regularly. Mag needs are so variable with cannabis, I'm used to supplementing epsom according to the specific strain/pheno.

 

[Budley Doright]

I have to admit, I'm limited in diagnostic abilities. It does look slightly different than a classic mag deficiency.

I've been using Lucas formula variants for 15 years and Mag is the only deficiency I've had regularly. Mag needs are so variable with cannabis, I'm used to supplementing epsom according to the specific strain/pheno.

There isnt a lot of difference in magnesium def and Potassium..... just the damage to leaf margins....

You might consider moving to jacks 5-12-26 and calcium nitrate.... its more suited to cannabis than most of the ferts that might be used with lucas....

Jacks contains more than 6% magnesium and 8% sulfur.....

There are folks who say they made jacks 5-12-26 specifically for cannabis.....

 

[Douglas.Curtis]

There isnt a lot of difference in magnesium def and Potassium..... just the damage to leaf margins....

You might consider moving to jacks 5-12-26 and calcium nitrate.... its more suited to cannabis than most of the ferts that might be used with lucas....

Jacks contains more than 6% magnesium and 8% sulfur.....

There are folks who say they made jacks 5-12-26 specifically for cannabis.....

Appreciate the info and will keep it in mind. I'm actually happy with tailoring the mag for each strain/pheno, since I'm extremely cautious of overfeeding any element. Since mag is the one huge variable, using the lucas nute profile gives me the basics for nearly any strain.

You can chop my flowers at any time throughout flower and quick dry. You'll always get a soft and fluffy, off white ash and no sparking or cracking.
when burned.

Just hasn't done much for teaching me deficiencies.

 

[Loc Dog]

Appreciate the info and will keep it in mind. I'm actually happy with tailoring the mag for each strain/pheno, since I'm extremely cautious of overfeeding any element. Since mag is the one huge variable, using the lucas nute profile gives me the basics for nearly any strain.

You can chop my flowers at any time throughout flower and quick dry. You'll always get a soft and fluffy, off white ash and no sparking or cracking.
when burned.

Just hasn't done much for teaching me deficiencies.

This is the best guide I have seen. It is hard for someone to determine what is wrong, when they are just shown pictures, with no idea of PH, PPM, moisture level, humidity, soil/coco/hydro, etc.. This covers all of those variables -

https://www.icmag.com/ic/showthread.php?t=11688

 

[Budley Doright]

Appreciate the info and will keep it in mind. I'm actually happy with tailoring the mag for each strain/pheno, since I'm extremely cautious of overfeeding any element. Since mag is the one huge variable, using the lucas nute profile gives me the basics for nearly any strain.

You can chop my flowers at any time throughout flower and quick dry. You'll always get a soft and fluffy, off white ash and no sparking or cracking.
when burned.

Just hasn't done much for teaching me deficiencies.

I was a mentor on Overgrow..... and spent most of my time in sick plants..... I helped Stitch with her sick plants stuff..... she did some things that werent exactly scientific.... some of her pics are most likely dead wrong.....but she published a book and I didnt....

You would probably do better to go to the Canna USA site they have a sick plants guide there....I was too close to how Stitch came up with her pics to recommend they are accurate...

As far as your ferts.... if they work for you thats all that matters....

When I mentored sick plants.... most of my customers were organic types.... or rookies...... Instead of using a fert system used by many others successfully....they did their own thing......

 

[Loc Dog]

I was a mentor on Overgrow..... and spent most of my time in sick plants..... I helped Stitch with her sick plants stuff..... she did some things that werent exactly scientific.... some of her pics are most likely dead wrong.....but she published a book and I didnt....

You would probably do better to go to the Canna USA site they have a sick plants guide there....I was too close to how Stitch came up with her pics to recommend they are accurate...

As far as your ferts.... if they work for you thats all that matters....

When I mentored sick plants.... most of my customers were organic types.... or rookies...... Instead of using a fert system used by many others successfully....they did their own thing......

Just looked at the disease section on that site. Can hydro get fusarium??? I just had coco crop ruined, and really paranoid. Would be easy to go back to flood and drain or RDWC with hydroton, if lower possibility of getting it. Currently trying Mycostop and trichoderma viride.

 

[Budley Doright]

I think you would be safest going rdwc..... fusarium is temp sensitive.....

keep your water under 70 degrees and treat with hydrogen peroxide and you should be fine....

 

[Loc Dog]

I think you would be safest going rdwc..... fusarium is temp sensitive.....

keep your water under 70 degrees and treat with hydrogen peroxide and you should be fine....

How much 3% H2O2 per gallon, and how often?

 

[Budley Doright]

How much 3% H2O2 per gallon, and how often?

Thats out of my expertise.... you should probably research that one yourself....