Paph. St. Swithin bud

I was really holding my breath since I noticed this bud and didn't want to jinx it by posting pictures but can't hold it anymore.
Here it is, a new homemade real bud developing on my Paph. St. Swithin:



My worries are concentrated around the humidity now. Both of my multifloral paphs live on the windowsill with south-east exposure. Glass has protective film to keep plants from direct sun but they still get lots of light and it gets pretty warm around them. As a result - humidity is very low:



Now, I could probably move some stuff around in my larger orchid tank to fit plant in, but St. Swithin had pretty bad mites infestation last fall, so I am worried that mites can still hide there and orchid tank rules state - no suspicious plants allowed.
Therefore, the bud might die from dry air any day.
But the fact that it appeared is pretty exciting and means that:
a) my plant is not a stubborn non-bloomer (like some of them might be);
b) my windowsill has the correct environment to induce the spike.

Looking at the picture I wonder if the brown line on the bud should be there or it means that bud is dying. Hope it is by design.
I mist the plant often trying to not get any water on the budding spot but it probably doesn't help much with humidity around the plant.
Hopefully the bud will hold until the warmth comes and heat drying the air will be turned off constantly.