Orange "rust" on old and new growth

Please help!

Amnesia Haze Auto (although I can't be sure I was actually sent auto seeds because these things are still in vegetation at week 16

Potted outdoors in soil

Watered a 2-3 times per week. Nutrients once a week.

It has been very hot where I am and I've been doing my best to provide protection from the heat (moving them into shade on the really hot days etc.). I have also swapped in seaweed extract in place of the regular plant food for the last two weeks.

I do believe the plants have been heat stressed. I came home from being away for a few days recently to discover some dry, crispy leaves. But this is different..

A couple of days ago, I began seeing this orange rusty effect happening on the edges of the leaves. It's now started to move across all of some leaves. This is occurring on relatively new foliage as well as old.

PH levels of the soil seems fine after testing. Could be slightly low, though. I am using one of those colour match test kits.

Any help would be much appreciated.

Cheers!

Looks like Ca def, although I haven't seen the edges look like that. I would add 1g (to a gallon) gypsum for Ca. Maybe 1g epsom salt for Mg.

az2000 said:

Looks like Ca def, although I haven't seen the edges look like that. I would add 1g (to a gallon) gypsum for Ca. Maybe 1g epsom salt for Mg.

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Thanks for the swift response and helpful info!

How time crucial do you think it is to act on this? They were watered and fed less than 24 hours ago, so there's a concern for overwatering if I give them the solution now.

Also, I have a suspicion that the soil PH maybe be slightly acid. Should I attempt to correct that before turning to the Ca and Ma supplements? I have some dolomite lime here ready to go.

Thanks again!

Schoob said:

How time crucial do you think it is to act on this? They were watered and fed less than 24 hours ago, so there's a concern for overwatering if I give them the solution now.

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I wouldn't chase it. Wait for the soil to dry thoroughly. The ph rises as the soil dries. A common problem is when people try to fix a problem and water too soon, keeping the soil too wet too long, holding the ph lower than it would be if they left it alone.

Schoob said:

Also, I have a suspicion that the soil PH maybe be slightly acid. Should I attempt to correct that before turning to the Ca and Ma supplements? I have some dolomite lime here ready to go.

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I wouldn't do anything on a suspicion. Why do you think it's acidic? You can google for "NCSU Pour-through runoff method" and be prepared to test the ph of your runoff next time you feed. It's kind of a time-consuming, tedious process. But, that would give you an indication of whether it's seriously low. (It's more definitive than measuring casual runoff.).

If you want to be more aware of your soil ph, you can spend $70 on a good soil probe (it's described in my sig).

If I were you, I would monitor my runoff ppms. That can tell you if you're overfeeding and/or not getting enough runoff. I.e. you could have acidity due to salt buildup. It's one of those things that you don't know what's too much until you hit that condition. But, it's handy to have the numbers if/when you hit the condition so you know where it's at and how to manage it (reduced strength, more runoff). For me, 2500ppm runoff is when I get lockout. My nutrients, soil, etc. comes out to 1600-1800 by early flower. I try to keep it there. If it reaches 2000, I reduce strength or mix more volume for more runoff. If it reaches 2200, I feed water only (with runoff).

I don't monitor it much now. Maybe 2-3 times during the grow. My "style" is dialed in.

I think the numbers will be different depending on your soil and nutrients. But, that gives you insight into what's happening if a problem like that is arising. (It's better to see the trend instead of looking at it now.).

Great info mate. Many thanks!