Need help with my lady slipper

[sii]

Hello all,

I bought this lady slipper last summer. It was in bloom for a short while. Can someone tell me how to encourage it to grow?

I live in Ontario and all my orchids sit by an east window. I water once a week and alternate with an organic fertilizer that contains 2 percent nitrogen, 2percent phosphoric acid 7 percent potash and 55 percent organic matter. I also have the Schultz orchid food (19-31-17)
What am I missing? What size pot should I use? I have bark, moss and hydro ton beads.
Thanks