Recurring bacterial? issue with Cattleya leaves

[bethmarie]

My two Hazel Boyds came from a group of 20 or more at the greenhouse. All of them had/still have this issue. Any ideas for treatment or prevention?

* black areas affect only new growth and usually appear once leaf is open.

* sometimes spreads and requires removal of part of leaf. other times doesn't spread & leaf matures normally, but marred by black areas.

* not a result of water sitting on leaves--I'm diligent with these plants.

* air flow is constant and sufficient in the growing area. I experimented with an additional small fan close to these two catts for a while. Had to water more often, but no effect on appearance of black spots.

* I've had these guys for a year or so-- none of my other plants have been affected.