Phalaenopsis leaves yellowing

[harpspiel]

I have a recently purchased Phal. 'Sogo Gold Tris' (a miniature equestris hybrid) which I placed in a terrarium. Over the past few weeks, at least 5 of its leaves have yellowed and fallen off.

The terrarium has compact fluorescent lighting (the plant is about 20" away from the bulbs), humidity between 50 and 80% and good air circulation provided by fans. The temperature is 68 at night and 80 daytime.

When I was moving the plant it was in bloom, and both buds and blooms subsequently wilted and fell off (except for one bloom, which it retained). I figured this could be from the stress of the move. But then it began to lose leaves from the bottom up.

The plant had at least 8 leaves at the beginning. Each leaf yellowed, starting at the base and working its way toward the tip, and then fell off. It even lost a new growth that was branching off to the side. The plant currently has only three leaves left.

I had it planted in bark chips, but they seemed to be retaining too much moisture so now the roots are exposed in the tank. They are healthy and green when wet, white when dry. I have been waiting for the roots to become white and then watering it again (that means every day or every other day).

I never have success with phals, and I simply cannot figure out what I'm doing wrong. In the terrarium with it are a Pleurothallis grobyi, a Masdevallia 'Copper Angel' and a Bulbophyllum harkerii, all apparently happy. I'll post pictures as soon as I have them.