Hey man,
Sometimes the most important thing in plant diagnosis is the approach....logical. 1st pic looks like classic C def to me......we keep that in mind. 2cnd pick looks like N has been moved from a lower fan leaf to be used by the growing shoot, classic N def....we keep that in mind.
You mention lucas so right away I think 0-1-2 NPK ratio and no N
You mention cal/mag "this week"
So that leads me to ask;
how much N in veg were you giving and when did you stop?
Did you add any cal during veg?
How much cal does your base nute mix have?
Are you in a media that is C hungry? like coir?
How do you adjust pH and with what reagent?
Calcium is important in the absorbtion of other nutrients. It regiulates proton pumps within the root that allow nute to be absorbed. Without C this absorbtion process is interrupted and you get phantom def issues. Furthermore, "bastic I believe has silica in it, yes? At very least it is very alkaline and has the potential to precipitate C from solution thus exacerbating the potential issue.
For anybody to say its this, this or this and heres how to fix it is folly....especially from a pic! But if you take the right approach you can often cover the most likely causes at once.
Clearly, at EC 2 you are not "starving" your plant. I have run EC's MUCH higher and seen fantastic results. However, it is often strain specific so.....
Your pH is fine. Period. Lockout do to fluctuating or "wrong" value is somewhat of a fallacy. 4.5-6.0.....several nute companies and a ton of gardens back this up.
http://www.flairform.com/hints/ph_optimum.htm
So, with all this to contemplate its most likely a Cal deficiency that is preventing proper nutrient absorbtion and that has led to various symptoms that cant be completely explained. Depending on your answers to the questions, I would also suspect a N def that needs approaching. Hope this helps. peace