Phosphorus Deficiency?

Always take pics of leaves on the plant. Random leaves tell us nothing. My guess, if your new growth is looking good, praying to the lights and doesn't have any weird coloration or patterns going on, that this is just common old leaf die off. Light only penetrates so far down into the plant and the foliage at the bottom will die and fall off because of lack of light. Totally normal. You judge the overall health of the plant by the new growth. A healthy plant is that rich blue green we all know and love. If the overall color changes from that....becomes too dark green or begins to wash out in color to a more yellowish green, the plant is trying to tell you what's up. A dark dark green foliage is one that is over fed/fertilized. The dark green is from nitrogen toxicity. A fading yellow green plant can mean several things, but usually that it's lacking something in the nutrition line. A plant that has been growing for a long time in the same container of soil, will use up the food in that soil (nutrients) and the color will start to wash out to a yellow green. Nutes are nothing more than plant food and only feed a plant. Light is the key element you need to force one to grow at the best rate and produce a maximum yield. You can pour chemicals into one all day long, but if you don't have sufficient light, you'll never get any kind of a yield out of a plant. We use 4, 1000 watt HPS fixtures per flower room, approx 10 x 12'. I generally run 2 plants per lamp so each has plenty of room to spread open during flower and light can penetrate as deep into the plant as possible and develop out the lower buds on the inside. We run a 10 week cycle and have been average around 5 - 6 oz per plant after cure. Not setting any records I'm sure, but the quality is superior and the buds are all nice and fat and dense and dripping with resin. It takes a while to have it all make sense. But by the time you run 2 or 3 plants through, it will begin to make sense in your head. The more you grow, the better you get at it. But put your money in your lighting always. Without it, you'll never be happy with what you produce come harvest time. The more you grow, the better you get at it though. In time, it's just a constant repetitive cycle. Best of luck. TWW

 

I'm in an area with extremely soft water. For a year my plants would die from the bottom, up. Twisted, curled under growth. Eventually death, or airy, poor quality buds, with a powdery coating over the stems. I read where I needed to add Cal/Mag to every watering until my tds meter read between 100-150 ppm's. Then nutes to the correct ppm for the plant stage,( or half the ppm to be safe). Then ph. I lost the bad growth, and the new growth turned around within a week. Pics are my leaves at that time.


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I'll start off by saying I'm a newb so if I'm completely off base here I'm sorry. Just out of curiosity have you inspected the underside of the leaves thoroughly for thrips and aphids? I agree that most of the leaves look like a nutrients issue but a couple on the right side of your first picture that are more on the green side have a few tiny white squiggly trails patterns on them, which could indicate a pest. Also since you mentioned it's mostly the lower leaves, this would also be consistent with a pest as they like to hide on the underside of the lower leaves in more a more shady spot. Anyway just wanted to share the thought.

 

That sure looks like phosphorus deficiency to me. Cannabis like up to twice as much phosphorus as nitrogen.