Now that light thing isn’t a piece of information that I have heard or read. All I knew is that a light too close can burn or bleach the leaves. And the issue was actually with the leaves about half way up the plant so that’s another reason I believed light was a non issue.
Also from my knowledge, mobile nutrients will show on the bottom while non mobile nutrients will show deficiency at the top and calcium is a non mobile nutrient which is where my idea of a calcium deficiency came from.
my city lists the water ppm at 100, so I’d imagine it is pretty close to that and I do not use well water