To be honest, I find Bird of Paradise is not a good indoor houseplant. In its preferred environment it likes high humidity, good drainage, lots of light access to even full sun conditions.
Looking at your plant, it is suffering from poor light conditions. Insufficient watering is also causing its decline. Remember this is a high humidity plant, so it can take in frequent watering. But that being said, with insufficient light it is hastening decline since water is not being used up efficiently as well.
You could improve the soil, try to add more pumice to it. It likes a moist media, but it has to be well draining too considering it is growing in a cramped little area, that is not drying up efficiently either, which rots the roots in the end.
Kyry's area is a nice place to grow BOP, since San Francisco weather is always amiable and milder to plants.
We all have varying growing locations so sometimes you just got to find that particular thing to improve. In your case kdl_, the thing you can improve is the water drainage aspect and the light aspect. Position that plant at level to your east facing window. Raise that container higher, it wants to feel better warmth and light, and well draining moist media.
