Lighting Is this why we NEED calcium added to our LED grows?

[Dr Fluff]

@arty zan , thanks mate! I appears my sinister plan to project knowledge beyond my actual scope is working perfectly,... ...
I've not dug into this for a while now,... still don't have any idea, but more and more anecdotal evidence keeps piling up! For sure, certain light companies seem to have issues with the severity of the problem,... One would suspect light distances and the other usual contributing suspects to be in play with this too, but in some cases, those are all in the green, and with side-by-side tents using other type of lights (QB, COB), it's seems lesser in manifestation, as much apples-to-apples as one can get,... blurple appears to be the worst culprit... I suspect there's a specific wavelength(s) behind this, maybe too much of it? Many folks overlook the limitations and problems with single wavelength diodes, and the absolute need for proper distances... too close and the blending is lost increasingly in kind, making for uneven blasting.... Of course, COB's and QB's don't have this issue....

Great post buddy!
I love your thinking.
You say blurple is the worst culprit and is the pretty much the oldest tech too.
When we look back at blurple light the main colours were blue LED's (in the 450nm to 470nm approx) and red LED's (in the 640nm to 680nm approx) which gave us a blurple colour.
Targeting the photosynthetic peaks of veg and bloom.
There are other processes that go on such as cation exchanger in the ADP cycle. ATP is often referred to as the "molecular unit of currency" of intracellular energy transfer. When consumed in metabolic processes, it converts either to adenosine diphosphate (ADP) or to adenosine monophosphate (AMP).
It maybe that a fuller spectrum is beneficial to the ADP cycle and so a fuller spectrum light has less problems because all of the systems are working, not just photosynthesis part of the equation.
COBs & QB's often in the 3500K range have a much fuller spectrum. COB's are made from "BLUE" LED's which are the most efficient LED's. These blue LED's are then coated with a phosphor coating to change the Kelvin of the LED.
Although the base LED's in COB's are called "Blue" It is really a "Spectrum" in which the prominent colour is blue, however it actually contains all the colours of the spectrum. Different phosphor coatings then produce the various Kelvin temperatures.
This give the COB a fuller spectrum with a lot of light in the green part of the spectrum.
Green light was once thought of as useless when it comes to growing plants but research in recent years has show that "Bright Green Light" Punches through the cells and and actually aid photosynthesis and possibly other cycles and systems.
Lights that use individual LED's have an optimal height to get the correct colour blending, which as you mention is important to get the best results.
Something @DutchPassionTony mentioned is that because LED's (modern LED light's especially) Have fuller spectrum or even and actual "Full Spectrum" more akin to the suns full spectrum.
This means the plants work harder and use more nutrients meaning it is easier to get deficiencies.
Just thought but should full spectrum LED lights, have their PH of their nutes be better targeted at each stage of growth the Plants are in.

Green chart Soil - Blue chart Hydro/coco
I'll give an example for the hydro chart as it has been ages since I grew in soil and can't remeber optimum ph for soil of the top of my head, right this moment.
So it is generally agreed that in coco the optimum PH is 5.8 PH (of course this should be allowed to range up and down a little within the parameters of 5.5 PH to 6.5 PH or thereabouts).
However 5.8 PH barely touches the Cal & Mag range where it becomes usesable.
Add in to this that coco is a calcium hog and we can see where problems might occur.
Another factor is incorrect PH'ing can debuffer the previously buffered coco and once again calcium is locked away.
Seedling like a more acidic feed and in to flower the PH needs to range towards the high end when it is heading towards the finish.
This maybe a bit rambly as I just typed of the top of my head but I hope it has some semblance of sense to it!