fungus spreading?

[fredr]

This fungus stuff is killing me. This spring I repotted and divided practically everything I have. I disposed of all old media and practically made all pots new again. I've been running into what I guess is black rot here and there on new growth. I bought some rather expensive BANROT to spray and even dunk my plants in it. Perhaps it takes a while but I'm still getting die off on new growth as it tunrs black. I have now covered my shade house to protect against the daily rain so that the orchids have a chance to dry out. I use cocohusk or aliflora as medium mixed with charcoal. Sometimes I mix the aliflora with the coconut. I know I just have to keep working this and hate to throw out a plant that has blackrot. I just cut off the affected part down to where it started to grow and hope for the best. Is this accepted policy or is the plant lost? The strange thing is other parts of such an orchid look good. Is the rot at the root level or only in the new growth. Here's a picture of one plant I just photographed. I then cut the bad stem off and have the pot standing on its own under roof. But others ar near other healthy plants. Can they hurt them even though I spray everything?
Note the black shoot on the right and a new good one on the left.
Just looking at the picture, I'm using bark here.