Jackie, I also think that Camille has diagnosed the problem. Below I have quoted directly from Orchids to Know and Grow, by Thomas J. Sheehan and Robert J. Black (because it's the book sitting my my computer):
*Botrytis is an ever-present fungus as it attacks not only living flowers but also dead flowers and foliage. Hence, it is extremely hard to keep the greenhouse free of Botrytis. Immediate removal of dead flowers and leaves will cut down on the source of inoculum. Botrytis spores require moisture to germinate; once germinated, they can quickly penetrate the tissue. The first signs are small, circular brown lesions on the sepals and petals, which enlarge slightly over time, but usually do not coalesce. Unfortunately, once the spots appear the flowers are marred for life. Keeping flowers dry with good air circulation will greatly reduce or sometimes prevent an infestation.*
Because your flowers appear to have coalesced brown areas it is possible that this is some other form of flower blight; still, I strongly suspect that it is fungal and most likely Botrytis. I'd urge you to cut off any and all flowers that even suggest the appearance of the infection, and then treat the plants with a fungicide. I know from other pictures you've posted that this could mean losing a LOT of flowers but I'd rather lose flowers this year to get them back next rather than risk the entire plant.
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