Culture Question on N Houmeiden

[Shoreguy]

How do I get Houmeiden to display its main characteristic (in addition to ruby root tips which for me is easy to get) of white inner variegation on the top surface of the leaves?

I do get white on the reverse side near the base.

I know it is a cultural issue for me and not the particular clone's fault as I have purchased several displaying the desired white inner variegation which then fades and never returns nor do new leaves ever develop the inner varigation on the top surface.

I have not been able to figure this out for years and it’s been frustrating.