Brown/Rust markings on leaves. Any ideas?

Need some opinions on a leaf issue I have. Can't figure it out. Any ideas would be much appreciated. Quite distinct markings.

This leaf is about half way up the plant. Newest leaves have signs of rusting too.

Thought it could be potassium deficient, pH fluctuation, calcium/magnesium, light burn.

Now starting to think it's nutrient burn as ive tried correcting everything else but to no avail.

Happening on 2 plants. Both afgan kush. Have 1 Top Dawg which shows no signs of any problems.

Thanks in advance!

Day 28 of Flower
Afgan Kush

In Canna Seed Mix soil with 20% perlite.

250w HPS

Day temp : 25c
Night temp : 19c
Humidity : 42%

pH : 6.2
EC : 0.8

Canna Flores
Canna CalMag at 0.4EC.

Looks to be like a magnesium deficiency perhaps. Are you watering with tap water or RO water?
Using CalMag at 0.4 EC seems like plenty so it's unlikely its a calmag problem but it does kind of look like it. Let's see what others say.

I was originally watering with demineralised water, now using tap water that's left exposed to the air for a couple days.

I'm always using Canna Cal/Mag at an EC of 0.4 - 0.5

Thank you for the quick response. I appreciate your knowledgeable opinion.





What are other members opinions?

Thanks in advanced!

Going to flush the plants out tonight with pH 6.5 water and CalMag at 0.5EC as they need watering today anyway. No flower nutrients

Potentially Mg has been locked out for some reason even though I've been using it from the start. Too much K potentially from my flowering nutrients as ive been increasing it slightly with some PK13/14.

I'll update this thread in a couple of weeks to see if it helped. As it may well be useful to someone at some point.

Jetlifeuk said:

Going to flush the plants out tonight with pH 6.5 water and CalMag at 0.5EC as they need watering today anyway. No flower nutrients

Potentially Mg has been locked out for some reason even though I've been using it from the start. Too much K potentially from my flowering nutrients as ive been increasing it slightly with some PK13/14.

I'll update this thread in a couple of weeks to see if it helped. As it may well be useful to someone at some point.

Click to expand...

What I suspect your problem may be is pH lockout of calcium, I do not know the soil you're using, but if it is in fact a soil then your pH is too low and you are likely locking out your calcium (and magnesium) you should adjust pH to 6.5 in soil for best results

The soil I'm using is Canna Seed Mix.

It has a pH out of the bag of 5.7

My pH run off varies between 6.0-6.5

I'll do my best to keep it above 6.5 going forward. Hopefully this will correct the issue.

I'll update in a couple weeks time.

Thanks for the responses.

Jetlifeuk said:

The soil I'm using is Canna Seed Mix.

It has a pH out of the bag of 5.7

My pH run off varies between 6.0-6.5

I'll do my best to keep it above 6.5 going forward. Hopefully this will correct the issue.

I'll update in a couple weeks time.

Thanks for the responses.

Click to expand...

Forget runoff pH and trying to adjust it in soil.

hotrodharley said:

Forget runoff pH and trying to adjust it in soil.

Click to expand...

Thanks for the reply.

Could you please elaborate?

I can test the soil pH tonight properly. Not just the run off.

How do you suggest is the best way to measure and then alter the pH if required in soil?

Thanks in advance

Jetlifeuk said:

Thanks for the reply.

Could you please elaborate?

I can test the soil pH tonight properly. Not just the run off.

How do you suggest is the best way to measure and then alter the pH if required in soil?

Thanks in advance

Click to expand...

Don't bother testing either. pH adjust your feeding per the feeding schedule. Then go for it. Do not overwater. Very important. Measuring runoff EC of PPM can be useful. Runoff pH is wasted time.

Add some dolomite lime to your medium next time and forget pH after that.

Thanks for the messages. All great advise and will certainly take it on board for next time. Particularly adding some dolomite lime into the soil.

However, I still don't have much advise on how to resolve my current situation in day 28 of flowering.

From the previous messages are you suggesting I just pH my feed and don't bother checking my soil pH from now on till harvest? That seems rather optimistic. Or I'm being pessimistic.

Thanks in advance

Checking runoff is the newest hippie myth.

No I'm just kidding, but this new obsession with it is, or at least seems to be? I check my run off once in a while usually in late flower and only if I suspect a plant has an issue (or if I'm bored).

Jetlifeuk said:

Thanks for the messages. All great advise and will certainly take it on board for next time. Particularly adding some dolomite lime into the soil.

However, I still don't have much advise on how to resolve my current situation in day 28 of flowering.

From the previous messages are you suggesting I just pH my feed and don't bother checking my soil pH from now on till harvest? That seems rather optimistic. Or I'm being pessimistic.

Thanks in advance

Click to expand...

You're almost halfway through flower. A good bloom feeding with cal mag. KISS.

hotrodharley said:

Add some dolomite lime to your medium next time and forget pH after that.

Click to expand...

Seems my pH is indeed low in my soil. Most likely the culprit in this situation.

How much dolomite lime do you tend to add?

Seems the consensus online is around 2 tablespoons per gallon of soil.

I'm interested in how much you guys like to add.

Thanks in advance!

Jetlifeuk said:

Seems my pH is indeed low in my soil. Most likely the culprit in this situation.

How much dolomite lime do you tend to add?

Seems the consensus online is around 2 tablespoons per gallon of soil.

I'm interested in how much you guys like to add.

Thanks in advance!

Click to expand...

Beachwalker said:

Click to expand...

That's doesn't seem to be of much use.

If you could answer my question, that would be more appreciated.

How many tablespoons of dolomite lime do you add per gallon of soil in your grows?

This would be useful information going forward.

I do not plan to implement it now, but for the future grows.

Thanks

Jetlifeuk said:

That's doesn't seem to be of much use.

If you could answer my question, that would be more appreciated.

How many tablespoons of dolomite lime do you add per gallon of soil in your grows?

This would be useful information going forward.

I do not plan to implement it now, but for the future grows.

Thanks

Click to expand...

A tablespoon per gallon is a good start.

hotrodharley said:

A tablespoon per gallon is a good start.

Click to expand...

Hot rod Harley.

Thank you for your short, concise answer. Exactly what I was after.

Thank you

buddy.kindbot.io finds spotting and burned leaf edges as a sign of potassium or calcium deficiency
try a couple photos to help narrow your diagnosis