Wow - I am sooo sorry that this has happened to your collection.
And it sounds like that came on quick!
I am not knowledgeable about disease like others, but I would be sure and find out what it is before I add any more to the collection. I am sure someone here will help better than me, but I would immediately flush with hydrogen peroxide and hit it with a fungicide just in case.
Some questions - What temp are these being kept at? And, from the photos it looks like there is color striations or bands of light and dark, in the leaves - is this true, or a result of the flash? And last - are there light grey spots on one of the leaves or are these the sunken spots you are mentioning?
Steve