Sorry soul-slayer, just seen this thread. Don't you just need tw@ts like that above !!!
Your problem sounds like that you've had whitespot and it's gone a bit too far. The fungal infection is usually a secondary infection after the whitespot.
The only way to get rid of it is by very aggressive treatment using some nasty chemicals (formalin and malchyte green (FMG))
Leave the pond with no fish in now and restock in spring....slowly using a good fish shop. Make sure the fish are nice and healthy and feeding well before you add any more and then only add a couple at a time.
Do you have a filter and UV ?....might be worth investing in one if you don't as these diseases are often down to poor water conditions.
Hope this helps a bit