Rhynchostylis is definitely slow growing and there is nothing you can do about it except letting it settle. I bought my Rhynchostylis gigantea as a very small plant and I couldn't see any real growth during the first year. If it had continued like that I think I would have tossed it. It took until the second year when I could see roots attaching to its wooden basket and it was as if that was necessary before the youngest leaf could develop further. The first flower stem came four years later but it was worth the wait. It still grows ridiculously slowly but I have accepted it now. I have also noticed that any visible growth only takes place during the warmest months of the year.