Odd Darkening of Leaves

Hi Everyone! This is my first grow, you can see my grow log at https://www.rollitup.org/aerogardeners/633232-ak-47-lowryder-autos-aerogarden.html In the past 1 1/2 weeks I have noticed the lowest leaves on my girl are beginning to darken This is an aero grow, and I have started them on a low nutrient diet of at 130ppm as of last week. I just up'd it to 350ppm a few days ago. There is no signs of nutrient burn on any leaves other than these darker marks on the these three low leaves. Any thoughts on what this could be? It just doesn't seem like the typical burn that I have been seeing on the forums. Your help is appreciated!

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Looks like nitrogen toxicity. To much nitrogen in your nutes. Going by just the pics thats my guess. Hope it helps.

my rule of thumb is cut the nutes in half of whats recomended and flush every third time until they straighten up ... then you can try full nutes again... i use promix as a medium however... you really need to check out the aeroponics section for the best help