az2000
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Well #3 is showing the same signs as #1 and #2 have and #3 has been is FFOF since the start.
When you said organic, I thought you meant a composted soil. I'm not sure Fox Farms qualifies as that. I get the impression it's more like amended (readily available) nutrients, not composted goodness. In your case, runoff might be good to get rid of the excess salts. Measuring the runoff ppms should be useful. I would do that before I start adding more salts to the soil. It appeas Fox Farms is slow drying. If you're keeping it too wet (which people often do), that can acidify the soil, limiting the uptake of nutrients. If the soil is too nutrient rich, that can be salt buildup. What looks like a deficiency could be from lockout. Adding more salts would make that worse.
Also, if you think it has Mg def, you can use epsom salt. 2.5 to 5g/gal is a good strength to treat a deficiency (depending on whether it's slight to severe). In that case you're only treating the deficiency, not adding calcium when there's no sign of needing it. If the deficiency is related to a Ca:Mg imbalance, adding Ca (with "calmag") would perpetuate that.