Increasing brown patches on leaves

I 've just purchased a 4-feet tall michelai maudiae and put it in a east facng deck to avoid direct afternoon sun. I found brown patches on some leaves. The size of the patches is increasing and that worrries me.
Any advice on watering schedule, soil type, light...; any info on the plant profile?

 

Probably mildewing.

 

What is mildewing? What causes it? any cure?

 

I think Ron ment Mildew (or mold)
your probably overwatering.