They're not super fast growers, and require lots of heat and humidity.
The coloration of the leaves is perfect for a bellina.
If my memory is correct, you mentioned having borderline night temperatures for those hot growers.
In low land Borneo, they don't see temperatures inferior to 77°F; so my guess for lack of flowering and slow-ish growth is that they need to adapt to your conditions, and your nights might be too cold.
More info about what makes Yin's Black Eagle:
https://bluenanta.com/detail/1001610...=98017&tab=sum