I haven't seen that before. I would guess it's due to inadequate watering. I can see healthy new roots growing. Just increase your watering and the plant should do well. Vandas need a lot more water than many people realize, but they also need good air circulation to the roots. Some people in very humid climates can pot them in large bark, and get away with watering once a week, but I have to water ones in large bark every 2-3 days.
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