Rust Spots mid-flower

[pg2052]

Hey all - started getting some brownish rust spots a few days ago...and they seem to be popping up with more frequency daily. Any ideas? Leaves seem to be curling up a touch now as well. Maybe a magnesium deficiency? Epsom salt foliar spray ok in mid flower? Pics below (didn't do a great job focusing, sorry).

Grow details:

Medium/grow method: OF/Perlite; 3 gallon fabric pots.

Feed: 1/2 dose of Fox Farm Trio (just cut out the Grow Big last feed); full serving of CalMag every other feed (was doing 1/2 serving, but just upped it for feed last night thinking that might be my rust issue); 1/2 serving of Silica every other feed; 1/2 serving of Fox Farm Beastie Bloomz for last 2 feeds; full serving of Mammoth P. Last feed was 760 PPM, pH 6.3; runoff was 840 PPM, pH 6.3. Feed, water, feed, water (every other other day). Runoff to about 15%. I flushed with pH'd water 2 weeks ago -- just to reset the medium a bit (per soil schedule).

water source: city water; runs a little acidic, so usually have to PH down to about 6.3-6.5.

Strain/age: Blueberry Auto ILGM. Week 9. Been flowering for about a month I guess.

Light: HLG 260xl - about 18 inches at 160 Watts; 20/4 light schedule

Climate: Indoor Tent; running a Cloudline T6 inline exhaust fan with Carbon Filter; passive intake; couple desk fans pushing air around; Temps: 75 during the day; 65 at night; RH: 38-48.

 

[pg2052]

After doing some digging, now I'm kind of wondering if it's a calcium deficiency. I'm thinking maybe a calcium foliar spray could help? Anyone ever try this stuff?

Amazon product

 

[Proph]

Calcium foliars are only a temporary fix. What you're seeing is a nutrient lock out.. Too much calcium locks out magnesium.. Too much magnesium will lock out calcium and potassium.. Too much phosphorus will lock out iron and zinc.. Signs of deficiencies do not automatically mean to add more of something. Especially with autos. 9 times out of 10 it means there's something in excess.

 

[pg2052]

Calcium foliars are only a temporary fix. What you're seeing is a nutrient lock out.. Too much calcium locks out magnesium.. Too much magnesium will lock out calcium and potassium.. Too much phosphorus will lock out iron and zinc.. Signs of deficiencies do not automatically mean to add more of something. Especially with autos. 9 times out of 10 it means there's something in excess.

I just flushed 2 weeks ago. My runoff last feed was 840 and my feed was 760; pH 6.3 in and out. Even with those facts you think I'm locked out? Would you suggest that I flush the plant?

 

[pg2052]

And if you think I should flush again, what would you suggest as far as feeding post-flush? Thanks for taking a look!!

 

[Proph]

I just flushed 2 weeks ago. My runoff last feed was 840 and my feed was 760; pH 6.3 in and out. Even with those facts you think I'm locked out? Would you suggest that I flush the plant?

If your plant is feeding correctly, the run off ppm/ec will be lower than the ppm/ec of the feed. If the plant is using the available nutrients then the ppm/ec will decrease as it does.. Im not really going off of personal opinion, I base everything on what the plant is showing verses how it's being fed... Any bagged soil will have enough calcium in it for an auto.. You've been adding extra calcium and magnesium weekly, when it wasn't needed.. That's where the nutrient imbalance began. Nutrient lock out looks exactly like deficiencies. Read up on nutrient lock out and how it affects the plant/ medium. It will make much more sense at that point. I'm not a big fan of "flushing" because autos have no recovery time for that type of root shock. I would just use water only for the next few days while checking the ppms of the run off.. Once it's in the 5-600 range I would start feeding again in that same range. Is there a reason you've been adding so much calmag?

 

[low_and_slow]

One of the reasons it makes sense to grow autoflowers is that their sensitive root systems do well in growing medium that doesn't need much fertilizer or many amendments. Looking at all the things you're adding into your Fox Farm, that would cause issues in even a hearty high-feeding photoperiod plant. My recommendation is to take a step back from all the additives, including base-fertilizers, and see how the plant responds to plain water between 6-6.3.

If you're getting 6.3 runoff in the 800's, something is SERIOUSLY wrong in the root zone. Like Proph said, just let her coast for a second and let's see where she gets.

My short list of what I see:
N-tox
Ca lockout
Overwatering
Heat/light stress (upturned leaf serrations)

 

[pg2052]

Cool cool. I’ll just hit with some water for a few days. Someone told me early on when I bought my hlg that I’d inevitably need to add calmag to my feed. So that’s what I did. Maybe a no no.

And what is it about 6.3 pH and 800 ppm that sounds like serious problem?

Thanks all

 

[BigB6]

Having the exact same issue. I was going to post my own post. Happy to see such good answers. This began for me after I used the biotabs pk booster tea. I also have been giving bio bizz calmag every feed. So it goes exactly in line with the answers given

 

[pg2052]

And just to clarify my question, I was mistakenly under the assumption that as long as pH and PPM runoff was pretty similar to what was in the feed, that I was in pretty good shape. Obviously I’m not understanding something about the correlation between ppm and ph. Tia!