Phal bellina var coerulea, growth stalled out?

[RandomGemini]

I purchased a phalaenopsis bellina var. coerulea in October. It was growing a single new leaf when purchased, once that finished growth has seemed to stall. I have seen ZERO root or leaf growth since.

I follow the same culture that I do for all of my phals. Watered when the medium is bone dry and I mist the aerial root when it's dry. I fertilize with better gro orchid plus at a rate of one quarter teaspoon/gal. I do this weekly.

I keep it in the same conditions as my other mini phals and they are all putting out new roots and leaves and several folks here just identified my first spike on one of my mini phals, so I must be doing something right for them, but not for the bellina. It's potted in bark in a square seedling type pot. I didn't want to repot it into slotted plastic until I saw some new root growth and I haven't seen anything.

Do bellinas have different temperature requirements from other phals? I have this sitting on a window sill with my other minis, but if they like to be warmer, I should move it. My other phals all seem to be doing well, particularly the minis, but this bellina has me concerned.

Any thoughts on what I could be doing to help this little guy along?

Thanks!