If this was my orchid I would get a systemic fungicide like thiomyl.
That is the only one that has stopped root and/or pseudobulb rot for me.
I also make sure I cut off all of the brown and yellow bulbs with cutters that I have flamed to make sterile.Cinnamon is great to seal the wounds. The only time I let relatives have orchids are the silk ones, or cut flower arrangements.
I did give my sister some who lives in Hawaii but her neighbor grows and gives her good advice!
He gave her a huge dendrobium and she told me she wanted to plant it in the ground and he stopped her!
GOOD LUCK!
