Brown spotting on Leaves.

Hi all, seems like I've spent most my time on RIU so far here in this section. I've noticed some brown spotting on 5 or 6 of my plants on a leaf or two each. Seems this is all happening on older leaves, not new leaves, and resembles Boron Deficiency. However I read about boron deficiency and most sources seem to say I'd notice graying new shoots, and new growth would be affected, but my new growth looks quite healthy.

Strains-- Purple White Rhino Kush & Critical Kush
Grow Stage-- beginning 4th week veg
Light-- 1000 Watt Metal Halide
Nutrients-- None (showed signs of nute burn at low dose of Humboldt oneness 5-9-4 about 2 weeks ago)
Soil-- Fox Farm OF
Room Temp--70-77
Relative Humidity--18-22%
Room Sq Ft-- 25 LWH=(5x5x6)
Pests-- none known
Water PH- 6.8-7.2 when measuring tap water, slightly below 6.2 when measuring run-off

What do you guys think this could be? Perhaps time to start feeding nutes? Another problem entirely? I'll be flipping them into 12/12 in the next week and want to make sure my girls are in tip top shape before they start flowering!

try to give them some calmag , its seem's the beggining of some cal def

cal def.

Lysergicpt said:

try to give them some calmag , its seem's the beggining of some cal def

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How does it look like calmag?

Sire Killem All said:

cal def.

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And too you

I would feed again. 2 weeks along time with out feed. For that soil

looks like she needs some Mg, those rust spots are indicative of a Magnesium deficiency.

FFoF only got nutes for like first 3-4 weeks, cal-mag Def IMO is the most common and last of nutes most ppl use. i say use it early and use it often.

"Plant Magic" do a cal mag with extra trace goodies added in that your plant needs in all stages of growth . If you're suffering from and cal mag related issues, my fix has to been 200ml per 100l in Hydro. I tried less but it responded better to the full dose!

Your leaves are also looking a little light in colour - That's magnesium. Magnesium and Calcium go hand in hand because they're so close on the PH scale. They have often led to problems like yours for me

It'll put your PH up so keep an eye on it and it'll also change your PPM so equate for that when you add it. If a 1/3 dose doesn't fix it, you'll want the full 2ml per litre and let it do it's work.
You may then want to flush once the problems sorted so you don't mess up the regular feed. Replace flush with your feed AND the cal mag. Check Ph and enjoy

Edit: Apologies, your leaves are actually pretty green, it was the light in the top right one!

209 Cali closet grower said:

How does it look like calmag?

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not mag , but begging of some cal def, magnesium you would have discoloring bettewen veins wich you dont but , anyway , calmag will solve it .

but , also you shouldn't have that problem's with your soil . alltought your PH seems to be in a good range for soil , with that soil you shouldn't have any defiency's in micronutrients , something is locking is absortion because for shure that there is enought of it until harvest in your soil . you should try to figure it out. its odd.
I've never had micronutrients problems while growing in soil , especially a soil with wormscastings like yours.
whats the size of your pots ?

If he hasn't feed in 2 weeks. He will have a domino effect on deficiencys.

No need for calmag. Just a good dose of good nutes

Lysergicpt said:

but , also you shouldn't have that problem's with your soil . alltought your PH seems to be in a good range for soil , with that soil you shouldn't have any defiency's in micronutrients , something is locking is absortion because for shure that there is enought of it until harvest in your soil . you should try to figure it out. its odd.
I've never had micronutrients problems while growing in soil , especially a soil with wormscastings like yours.
whats the size of your pots ?

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Do you think something could be causing a lockout? I looked at PH and it seemed just a bit acitic which should have been right, and they certainly aren't root bound, still pretty small fellows for that. They do in some ways resemble mag def, a bit hard to tell the differences though, anyways I picked up this up from my local hydro store and just gave 2.5ml/gal (half strength) for their watering this morning, hopefully it clears it up.

209 Cali closet grower said:

No need for calmag. Just a good dose of good nutes

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I think there's definitely a chance they could be in need of some nutes. Will be starting with quarter strength 5-9-4 in the next week for sure.

209 Cali closet grower said:

No need for calmag. Just a good dose of good nutes

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yes it will probably solve it , it still just the beggining of if so probably you dont need to , but if you already have the calmag you could make a foliar feed right away , its works faster.

So I found a leaf in seemingly later stages of whatever the problem in the back of my canopy... Does this still appear to be Cal/Mag Def in its later stages?
I've started watering with CaliMag aswell as Humboldt 5-9-4 (their first feeding of Humboldt today, first Calimag yesterday)
What do you all think?

give it a little time, that one's toast- it doesn't repair. look at the overall plant- it doesn't look bad

Hey guys, I'm going to reopen this for opinions. The problem seems to have started to effect a few more leaves, I started dosing with 1/2 strength cal mag and 1/4th strength nutes. Any idea what else could cause this?

Go up to full strength with the calmag.
2ml per Litre
Make sure that your PH is sitting 5.5-5.8
Keep your feed at 900ppm and cal mag will take that up to about 1100ish.

Takes about 4 days at full strength to notice anything.

The damaged leaves will not generally recover fully. I remove them when i see them like your photo.

EDIT- You'll also notice on the NEW growth in that photo that the leaves are coming out green...not discoloured. I would still go full strength with your CalMag anyways.