Always, Always, Always QT your new fish. Having said that, did you say that the fish has pearlscales? Cause I'm not seeing pineconing... Maybe it's just my screen. What are you guys seeing that says dropsy to you? Dropsy is not contagious, it is a symptom of severe problems with parasites, liver, heart, or kidneys. Has the pineconing progressed?
I would try to get an idea of what I was treating for before I treated as well. Parasite treatments are dangerous and there is no cure-all. If you can, borrow a microscope and do a scrape. Treat for the most lethal problem first and go from there.
What is going on with the other fish? Be careful not to get worked up and start seeing problems where they don't exist. That's what I do, one fish acts funny and all the sudden I'm seeing problems everywhere. Good Luck, I'm hoping it's just pearlscaling we're seeing and nothing serious. Please keep us updated!