Introduced 2 male and 4 female guppies to the aquarium yesterday (182 liters, zebra danios, cardinal tetras, a few corys, heavily planted). They all seemed very lethargic, not moving too much but were actually eating some bloodworm. I thought it all just might be stress related, but overnight one of the males died, and this afternoon i noticed a white spot on the back of one of the females. See picture (sorry its not great quality). Any suggestions on what to do?