I am 90% certain that this is a Magnesium deficiency, but as I have never seen a Magnesium deficiency before, I would like some expert confirmation.

Babygro? I know this is your absolute favourite deficiency...

Thanks in advance!

If it is, the epsom salts are at the ready!

Oh and they are in soil, I've been feeding her a 5-1-1 Alaskan Fish Emulsion at 1/4 strength PH is fine, got 4 CFL's on her (2 23-watt daylights, and 2 42-watt soft whites) Temperature, humdity, etc... are all fine.

ETA: I realize the pic is blurry, but it's the best my shitty camera can manage. A description would be brown rust-coloured spots, and inter-veinal yellowing.

Attached Images

Linguini3wksMgdef.jpg (59.0 KB, 79 views)

Subscribing------------ I am using the same nutes. Babygrow also helped me figure out a good veg ratio. Good luck bro.

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Thanks akrmatona.

I also forgot to mention that she's ~ 3 weeks old. *just* started feeding nutes and I'm still a bit unsure about feeding schedules.

You can be feeding it full strength nutes. since that is such a low NPK. That also looks like it does have an MG deff.

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Thanks kieahtoka!

Would you recommend still stepping up 1/2, 3/4, to full, or going straight to full?

i personally would work up 1/4 per feed until at full strenght. any signs of burning and you know you need to back it off. the only time i've ever burnt a plant with nitrogen was with fish emulsion. the stuff is weak, but readily available, and so it can burn if your plants are not yet acclimated to it.

kp

Thanks KP! will do 1/2 strength next feeding, and step up from there.

Any thoughts on whether that's an Mg deficiency?

Yes, work your way up.

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An update: I added a teaspoon/quart of epsom salt my last watering, and the brown spots no longer seem to be spreading, which means that it probably was a Mg deficiency.

I also stepped up the nutes to 1/2 strength, but I'm starting to see some yellowing on the bottom leaves, which means i've got a nitrogen deficiency, so I plan on stepping up to 3/4 strength my next feeding.

Soooo basically, you were all 100% correct! Thanks so much for helping, and hopefully I'll be able to see the signs earlier & correct earlier my on my next grow!

Hiya Frankie!

Sorry I must have missed this, but fortunately others have confirmed your suspicions for you - it certainly looks like Mg to me. Is it between 4-6 weeks veg? If it is, it's definitely Mg - that's the time it'll show up.

The problem is, Epsom salts is only a fix to stop it spreading - it won't cure the underlying problem, which is often connected to your irrigation water.

The fish emulsion has a fairly low NPK ratio and as kp mentioned you can usually feed that at higher amounts than say a fertiliser with a higher NPK ratio, but a lot depends on the TDS of your irrigation water. My fish emulsion is recommended at 2-4 mil per litre, so you should be fairly safe at the minimum amount, or 1/2 of yours, but you're wise to start low as kp mentioned and work your way up.

Also bear in mind that the plant can take up to 7 days or longer to show signs of improvement after a feeding depending on how quickly it assimilates the nutrients so don't start going mad with the ferts if you see no improvement after a couple of days

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