Bletilla striata

Over the years, contrary to what others seem to experience, my bletilla striata, or Chinese ground orchid continues to grow leaves, but fewer and fewer flowers. Last year I dug up many, split them and replanted with high hopes, but was again very disappointed with the results. They are in a north front yard that gets full sun in the pm.
(I read now light shade is required); yet the old woman I got them from many years ago had them in her back yard in full sun, growing in a large clump in what had once been a veg garden. What am I missing?
Thanks for any and all suggestions...

 

How much fertilizer do you use, if any?

 

none; I dig up lawn and transform as I go...