[Tobi]

Srefka,
I believe you have a Phalaenopsis type Dendrobium. Alot of mine are losing
their leaves from the older canes right now. This is quite normal. At times
they will have these speckled black spot or patches of black before they turn
yellow and fall off. If there were mites you would see them moving with a
magnifying glass on the underside of the leaves along very fine webs. As
long as the new growth leaves are not experiencing this, I would not worry.
They also need alot of light, so I would move them to a south to southwest
window. Sheltered light in a southern window.