Rainy season in Indonesia this year starts at late October and will last by April. The number one enemy in the rainy season for growing orchids is snail and rot disease. Snail will eat root and spread out diseases. I used snailex (snail bait) for snail elimination every week.
Rot disease is cause by excess water on the potting media and very humid air. Fungicide such as Physan 20 will help to reduce the chance of rot disease. I use 1 teaspoon of Physan 20 diluted into 4 liter of water and spray every week to my orchid.