You mean Edawrd posted his R wallichii stopped growing and stunted when he added high Mg to 10ppm.

I tried this with the same plant, I found no such effect at 15ppm Mg.
Perhaps he had some other confounding effect he over looked?
Can he confidently rule this out?
No.
I couldn't.
It would still be in doubt in my mind.
He made a hypothese, I tested it and did not find it to hold true.
I'm not saying what stunted his plants, I am saying what did not.
That I do have much more confidence in than mere speculating the cause.........

My tap water in SB was a GH of 24 and had a Mg range of 12-20ppm.
I had no issues with many plants. I had more issues with CO2 namely.

But I could not discount other possible issues, so I had R wallichii when he posted it, added MgSO4.7H2O to get 15ppm, a good deal higher than the 10ppm suggested, the R wallichii still grew nicely.
At the time I had near RO like Tap, GH 1 and KH about 2.

I've seen the plant specifically stunt like the picture, and it was CO2.
But it might be something else and one thing causing another in his tank.

Maybe he should switch to EI?

Regarding ratios of Mg and Ca.
Nothing in the argiculture field suggest this is critical nor in aquatic systems as long as you do not get too far out there and have things become limiting.

My bet is you have issues with the CO2 and with the high KH.
Edward likes RO water and adds basically just enough, and seldom explores the upper ranges, believing them to inherent toxic, bad.

I'm more practical and willing to try odd things that most folks experience and run into. Many are not willign to buy test kits,RO etc, I know, I tried to ask folks to do it in the past.
See SFBAAPS for an old reference article.

There's more to aquatic plants than mere nutrients alone.
I also have had a lot of experience moving and dealing with a wide array of taps and tend to be somewhat anti RO for all my water needs, having seen and dealt with such issues rather than giving up and going all RO and instisting others buy test kits, calibrate, micromanage, must use RO water for the tank etc.

Rather than accepting weak inductive reasoning(I observed this, it must be true for all cases), seeing if the hypothese is false or true (actually testing and trying to refrute the hypothese) and stands up to further test allows you to make a much better judgement and tentative belief of what is occuring.

Then you can show to yourself what is and is not true in your mind and see what makes the most sense.

This might open eyes:

Inductive reasoning - Wikipedia, the free encyclopedia

Regards,
Tom Barr