My tap water is 0.4 EC, I used to go to around 1.0-1.1 once nuts mixed, I pushed it to 1.4 in last mixIf you ask me, it doesn't look like cal mag deficiency anyway. I figured somebody else would have said that by now. I think it looks like a K deficiency. I'm not familiar with your nutes and I didn't see your EC but they may need a little more.
My first idea was that it wasn't calcium deficiency but excess cause according to Metrop, I add mixed too much calgreen (which has calcium in it) in my nutrient solution, the dosage ain't the same in soil and dwc (3 times less in dwc) and I wasn't aware of it.
I fixed it like a week ago or more, still newer growth are getting the same spots.
Calcium excess can lockout other nutrients like K.
I guess I'm probably just going to try things and see what happen lol.
Still thank you for your answer, any point of view is interesting =)