I do not think it is leaf blight , more like overwatering for your conditions...but,
quoting from Native Orchids of Australia by David L Jones
"This species grows in moist to wet habitats, particularly permanent swamps where it may occur in extensive patches in black peaty soil. It also colonises localised depressions and soaks in open forest and grassland and is occasionally found growing on well drained sites.
Now some of the sites described above might have been almost dry a week or two ago because the wet season was late. Not now, everything is very wet.
Distribution in Australia, North Eastern Queensland to North Eastern NSW. Maximum rainfall Summer, Drier and less humid in winter, though rain can fall at any season.
Here, Sydney Australia you need a cold glasshouse or bush-house, I do not grow it because it gets too large. Pot in Cymbidium mix..
Seeing it is winter there maybe enlarge the drainage holes, and cut back the water slightly.
Good luck.

Maybe it is overfertilizing? My Phrags do that when I fertilize them with the other orchids instead of skipping a few feedings.

Both good suggestions. I just wonder why they looked so gorgeous right up until the flowers opened? Doesn't make sense to me that things would suddenly stop working. As an aside, I gave a few of these plants to a friend and his are doing the exact same thing (we had slightly different protocols).

It was not so much a suggestion, more an attempt to explain how this orchid grows in nature, and how you should modify your culture according to the seasons.
Only guessing that too much water and as Lisa suggests too much fertiliser are the cause of the problem. But where it grows in the wild no one is running around fertilising the plants every two weeks. The plants might get more nourishment in summer from rainwater bringing some nourishment into the places where it grows.
It is all a guess, especially so since you have nil climate or state information on your my page details.

This post was edited by arthurm on Fri, Feb 1, 13 at 21:08