There are these black spots on almost every leaf of our Dendrobium (?). It has flowered once but has kind of gone into a resting phase ever since, I guess that is normal (please correct me if it's not).
It is kept indoors, just by the side of a South facing window, so gets indirect sunlight the entire day. We water it once every 4 or so days and is fed water soluble NPK 20:20:20 every couple weeks.
The climate here is tropical so it is warm/hot and humid except for the few winter months of the year.
What are these spots and what should we do to prevent them?
Is it advisable to put it in a place where it gets direct sunlight for a few hours of the day?