Light Brown "Smudge" On My Cymbidium?

by Jim Walter
(UK)

Hi,

I bought a Cymbidium orchid last year,in a discount store, although it looked healthy, I must admit I didn't check it over fully.

It has developed light brown smudge like marks on the reverse of the leaves, I would liken it to a "rust" like diseases. It appears to be systemic, as 3 back bulbs that I germinated new shoots on have similar markings. None of my other orchids are effected, I thought I would branch out into Cymbidiums but am prepared to get rid of it if that is the only cure.