Yes! I am on steep learning curve here, never having had anything like this sort of problem in the past, The odd wasp attack depleteing a hive a to death or the odd starved colony but never loosing bees on this scale, 3 colonies hurts!! I will in future treat all swarms regardless and will let you know if I loose any more colonies, hopefully I should save the rest as I have purchased a vapouriser today, and will treat them tomorrow. I know I will sacrifice some brood but it's still early here so there shouldn't be too much, and at least I will save the colony.
I hope that is the right thing to do!?