I agree with BigBill, consider repotting, especially if you just got it from someone else. You need to make sure you get it in a proper mix and size pot that is suitable for the orchid. Plus repotting will give you a chance to cut off all the rotten growth that you don't need. Always watch out for over watering. Most orchids need water only once a week. If the roots look dark green and wet, they don't need it. Part of the reason I always prefer a clear pot so I can see the roots.
