I have tried different growing mediums for orchids. First was with cocopit and I noticed that many plants get easily infected. I tried fungicides, but not much help. What I have realized is that cocopit is good for other plants as it stores water and watering can be lessened.  But for orchids, it is very hard to  maintain watering.  So I am changing the potting medium to mainly charcoal, coconut husk and pieces of tiles and bricks. Let me see if it works.