Your first plants' roots look awfully dark, but maybe it's the lighting? If you have roots that dark on a vanda you should consider un-potting and giving it a good soak in something antifungal or some hydrogen peroxide if you don't have the regular stuff. Also, use a clean cutting utensil that can be sterilized or thrown away to remove any black or brown rotted roots. If left on they can infect other healthy roots and any plants nearby. After cleaning it up; I would sit that one on top of the medium and let it grow roots down. That way they will be suited for potting. Air roots don't do well being potted up. And if you don't already have fans pointing at these, you might want to purchase a small inexpensive fan and point it at the vandas. Good luck...I am a total vanda nut myself. They are wonderful bloomers when they are happy.