Colmanara Wildcat Green Valley

[quique1000]

I Just purchased a Colmanara Wildcat Green Valley in bloom and it was wonderful; the blooms lasted for 2-3 weeks.

It seems however that the plant is dying:
1. Its pseudobulbs are shriveled and covered with blackspots.
2. Its roots have rotted
3. One of the leaves turned yellow and fell off.

If roots have rotted, it seems too much water. However, that would mean smooth well developed psudobulbs.

I have it in the vicinity of a window, facing south (Washington DC climate), no direct light.

Can anybody shed some light?:

Thanks,