@Riddle, I have seen you give out some solid advice here on RIU, and in this thread, so I have a question for you (& others).
Got this deficiency, on upper leaves mostly, not really a lot overall, on Blue Dream. Am just now into week 4 of Flowering. All 100% coco. Canna nutes. A+B. Also used rhizotonic early on. have since stopped. started using PK 13/14 at 1/2 strength in week 2 & 3, and reg strength starting week 4.
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I was apparently using too much Cal/Mg, at around 10ml/gal of MagiCal. More than a week ago I was told that was high, so I dropped it down to 3ml/gal or something. I think only one feeding I did a small control group with some FoxFarm Beastie Bloomz, but that was only 4 plants I think. I only used the lowest strength they recommended, which is like 1/4 tsp/gal.. so I dont think I overdid it. But this came up FAST.. like in the last few days.
Thoughts?
{journal at my sig if you want to look back a few weeks, i didnt start the journal at Day 1 though :/ }