Calcium "deficiency" at 8ml/RO gal and still no improvements in weeks.. now my other tent has started the same spots.

hey there Blake, you're right that it's a cal mag issue even though you're giving them a ton of it. Why? because of the heavy light schedule the plant needs more calmag. Simply put it cannot absorb enough of it quick enough. That's because the absorption rate through the roots is like 20% efficient, what you want to do is make a spray with like 4ml /L and spray it on twice a week, that's because absorption efficiency through the leafs is 80% , compared to the roots with 20%. so that's why you want to do both. Hope this helps ! 🚀

I’m gonna agree with Roberts on this for sure.. does not appear to be calcium or magnesium deficiency. You rarely need more than 4-5 ml per gallon of calimagic IMO

Especially since your seeing the same thing in your other tent. If its minor in the other tent you might be able to control it by turning off all fans, Then carefully removing all infected leaves being extra cautious not to spread any spores. Leave the fans on low for a day or two and then do another inspection. It might be a good idea to segregate your visits to each tent with a change of cloth's and washing of your hands and any tools used.

Looks a little like "Septoria Leaf Spot" https://canvastsupplyco.com/blogs/news/identifying-and-controlling-common-hemp-leaf-diseases

If your PH is 6.5 (runoff pH?), light distance is 18 inches and you've been giving calMag then by process of elimination my guess is a potassium deficiency