Well, based on the information, here is an educated guess. Since these fish were new additions, they very easilly could have had parasites in the water they were in. Fish can stress when moved or well any other reason really. If they stressed they became more liley to fall to the diseases. Since you state that the issue has moved to multiple tanks I would venture a guess that you use the same cleaning equipment on both.. You water may still be stressing the fish. When you get the test kits we'll know more. Until then, I would suggest trying to get the affected fish into a med tank and isolate em. Treat them specifically if at all possible. If the entire tank is showing signs of illness you'll need to medicate it fully.. you may affect your bio filter.. just fair warning