Softer water seems to make both of these easier to grow IME.
It's not madatory, but they do better.

Color is better when we add more GH booster also but not KH.

This is a general consensus after what? 10 years of the local club growing and doing very well with the plant, Neil sending gobs of it for sale for over 20 years etc.

Other than that, high nutrients sends these plants into over drive.

I think CO2 is the most problematic issue for most folks having issues, and if that's not it, then it's just consistent dosing/CO2/routines/lower KH.

If you apply CO2 mist directly on the plant, they should grow very well in most conditions.(rules out CO2 as an issue)

Regards,
Tom Barr