Black dots on underneath only of Cymbidium hybrid

[thatawkwardguy]

Hi,

I have a Cymbidium hybrid with sinese in its parentage, it has black spotting on underneath of leaf only and it doesn't show through on to upper side of leaf and there appears to be no chlorosis etc. Anyone have any idea what it could be? I've attached a picture.

Thanks!

[WhiteRabbit]

Fungus, perhaps.
Hopefully some other members can add their opinions.