I was the one that first put forth the color change hypothesis with low NO3's in the hobby and then 3-4 of us shown it.
Others followed there after, but folks ran very low NO3 for a long time, they ran into issues when the NO3 bottomed out and with poor testign and poor test methods for such low NO3's readings.

So luck was involved in many successful cases. Lower light seemed to help, limiting PO4 was suggested again as a way to reduce the NO3 demand and maintain a low NO3 without stunting.

As fas as R macrandra getting stunted at high NO3?
Total crap.

I have it at 30ppm and it's a weed.
Always has been.

I'm not sure red color is desirable for plants though, they do not grow as well/fast, it's a sign of N stress in many species, not health.

Put another way:
Is a bony skinny 1/2 starved dog aesthetic?
Bony starved super model?
Starved plant?

Depends on your perception, all cases involved stressed animals/peoples/plants. How you rationalize your moral choice is more subjective, but I try to not make such conflicting choices if possible.

Many plants will do very well and look nice a red with higher GH's also as well as more traces, good CO2 and even less light.


Regards,
Tom Barr