Not sure if dipping is enough to kill all the tomonts. Have you ever had ick before in that tank? It can last a long time without severely affecting your fish if they are strong and healthy. But if stressed, that could prompt an outbreak.
Here is a good link that might give you some clues.
http://reefsanctuary.com/forum/index...d-facts.23132/
I have had ick problems in the past, but not since after QTing all fish and corals.