Update: so there has been some progression of the deficiency since my last post. Overall the plant looks good and is drinking the whole res daily. I feel like it's still doing quite a bit better than my previous grows. In my previous grows when this deficiency started to show it would progress pretty quickly..like close to overnight it would spread through the upper growth.
Regardless, I am a little frustrated to see it return and I would really like to understand why it's happening. I would welcome any one following this thread to chime in with any advice or thoughts.
I will include pics below to try and show what is happening. I believe this is a calcium deficiency. As evidenced by the symptoms and the fact that it always shows in the upper growth of the plant and calcium is an immobile nutrient.
Here is a shot of the whole plant
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Below are examples of the symptoms that have worsened over the last days
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From my research I think I have sort of narrowed the possible causes down somewhat. It seems that the most common cause of cal deficiency is low ph acidic soil.I dont PH my water, as it comes out of my well/tap at roughly 6.8. My soil is peat based so acidity is possible, but my previous use of dolomite and current use of oyster shell flour should address this.I should be testing my soil ph to really know but I am reluctant to shell out the $ for an accurate soil meter.and I dont believe that run off/ slurry tests are accurate enough to draw a conclusion from.
The 2nd possible cause could be an excess of another nutrient locking cal out. I could see it being a possible excess of mag from my use of dolomite. Any other nutrient exvess does seem unlikely to me as I always try to use my amendments at a reduced rate from recommended. A less is more approach. And I feel like I would see more signs of excess before this shows up, which I dont really see. The plants just do super well up to this same point around day 40-50 and then these symptoms show up fairly suddenly.also this is a big fast growing plant that seems like it should be a pretty heavy feeder.
That brings me to my third theory.. possibly this explosive growth is just so vigorous that I actually am not supplying enough nutrients? My homemade SIPs are only about 7 gallons of soil so its also possible that I just am not supplying the plant with enough cal to meet its needs?? I wouldn't suspect that as,I have a lot of sources of cal in my soil. My previous use of dolomite, current use of oyster shell, gypsum and worm castings. Also the gaia green amendments I use have several sources of cal as well.again tho I dont see any signs of the plants being hungry before this shows up?
Please chime in and let me know any thoughts you might have. It's a real head scratcher for me and I just want to understand why it's happening! I am confident that the plant will still give me a great harvest and as I said earlier it is an improvement over my previous grows.also would you try and address it? In the past I have tried several things to correct it mainly adding more calcium sources through top dress or even using a liquid cal/mag supplement with no improvement and maybe only a little slowing of the progression.
Also, interestingly there is no sign of it in the smaller plants
Thanks everybody for any input you might have