I'd be more concerned about the tips of the roots than the tiny black spots. Is this your first Vanda? And what sort of temperatures is the plant getting.
No idea how to grow anything in zone 7b but surely spag.
is not the best potting material.
No matter what you do the tiny black spots will be forever because they are scar tissue.
I am trying to grow "Vandas" with moderate success in a micro climate that is zone 10 and only have had some success with those that are "cold tolerant" which yours is because one parent is Vanda coerulea.
Good growing conditions and a cleanup with eco oil (based on canola and eucalyptus oils) every few months should prevent fungus getting a hold.
Anyway tell us more about your growing conditions.

Yes this is my first vanda. I water it once a week, i try doing it twice a week since it dries out pretty fast. I grow it on a north west window sill and under a grow lamp and the area around it is about 75/80 degrees. It gets to 70 at night. I was told by many people to keep it loosely in a basket with some coconut husks and many people had great success. I fertilize about twice a month with orchid urea free fertilizer.
O since i get sinus problems during the winter i always have my humidifier running in my room.

This post was edited by katsols on Tue, Mar 5, 13 at 2:24