Here is a link to a site with some info on diseases and treatment,

http://staugorchidsociety.org/culturepests-diseases.htm

It's hard to give advice on what to do since a lot of orchid ailments tend to have similar symptoms. My guess would be a bacterial issue, you can typically use the same treatment you would use for black spot on roses on your orchids.

What are you watering habits like, these things tend to happen conditions are cool and wet.

You may want to also consider the possibility of a calcium deficiency. I have had both issues. I found that upping the calcium and increasing the air movement helped fend off the infections. I use RO and rain water so my water needs a bit of assistance.

Environmental Ailments

Darlene and James, great links.

I always forget about the St. Augustine website and how many good articles they have. I'm having a problem with buds dying and haven't figured out how to deal with it. I'm going to use Cal/Mag again and see if it helps. Very frustrating problem.

Thank you,

Jane

Cool and wet was a good description a few weeks ago. Now the plants are indoors, so only get water when I give it. Thanks for the link James.

Darlene, Ive been using rain water regularly since we've been having good rains and my barrels are full. I hadn't thought of the good elements that come with well water. I will read your link too.

The Cal/Mag really helps with strengthen the growths. I have the biggest issue with these deficiencies during the summer when new growth is rampant. Still I supplement year round. Now I don't have new growths and leafs turning black on me.

Shelia given the wet cool wwater you described, your probably picked up and infection. I would treat as the site instructs for that. Of course, adding the Cal/Mag to your nutrient regimen be an additional support.

Jane, I forget about the St. Augustin site until with brownish-black turns up on my plants. Then I am reminded of how much great information is on the site.