Need help identifying if is a Mg, N or P deficency

Sick Plants & Problems
#1

Sup everybody, my plants are showing off some symptoms which to me look like a serious deficency, im in the last day of week four of flowering and everything was going well untill now that the yellowing on the lower leaves is going pretty fast in two of my plants.
Im not sure if is a N, P or Mg deficency so im asking for any experienced growers for more opinions, thanks in advance, here are some pics:

Plant 1) this one barely ia showing signs in one of the leaves so the problem in this one is not so bad, all the other leaves in this plant are green as they can get, but not the lower leaf, I noticed that the yellowing is coming from the sides also, this one doesn’t get me too worriedworried because is going slower than the other two plants but here’s a pic:

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Plant 2) this one was going really well and since two days to now the yellowing took over a few lower leaves and this one has some brown spots like drying in between the leaves:

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Picture of another leave same plant

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Plant 3) this one was the first to show signs of the deficiency which at the beginning I though it was Nitrogen def, but then I thought I give her some fert with N but still turning yellow in the lower leaves:

IMG_20180526_175251.jpg1868×3327 1.71 MB

Ohh btw, the plants are green and lush on the top leaves but plant 2 & 3 the yellowing is going faster.
Thanks for any advice.

#2

So you say the leaves are healthy and green at the top.

What are you using for lighting?

#3

I’m using a 300w Led grow light by Kingbo…

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#4

My first guess is that the light is not reaching the bottom of the plants, and so the plants will slowly consume all of the useful nutrients stored in the bottom leaves (slowly yellow and dry up). Can we see the top of the canopy too

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#5

Ok I tried to take pics using a cfl to level the colors of the grow light:

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IMG_20180526_182634.jpg4160×2336 1.93 MB

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#6

Move the lights in as close as you can.

You may want to invest in more powerful lighting for flowering.

The tops look just fine.

I would suggest you let the plants finish taking what they can from the bottom leaves, They look rough, but they are still serving.

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#7

Thanks, yes i know, I used to grow with hps/mh system in the early 2000’s when leds didn’t even existed, but unfortunately for now I can’t use hid lamps because I leave in southern Mexico and we have super high temps all year long especially now but for sure in the near future I will try to go back to hid lamps.
And yes I will not touch this yellow leaves untill the plant sucks them.
Thanks bro!

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#8

There are some very good quality LED systems that are cooler. They are not cheap, but they may serve you best.

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#9

I’d agree that there doesn’t seem to be enough light over the flowering plants, try sum side lighting with led off the shelf bulbs and CFL’s , and do you have a fan hitting the plants.? Remember that you can ‘burn’ your plants with a fan etc… If you can stand plants at your windows or outdoors I’d go that route, the sun is the BEST light…
Good luck with your grow mate ,
Gaz

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#10

Plants look good to me man kind of normal to see this on lower leaves as time goes on it’s a translocation thing with N but I’d steer away from any High N Inputs at this time P and K are what the plants are hungry for now with 4-6 weeks to go or so in your grow!

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