I just reread the initial post and must have missed the coral part. To be honest, I think that the sudden water changes you did after noticing fish deaths put all the parameters out of whack. It's possible that swings in alk, salinity, or even nitrates would put everything into shock. However, with this information, it also seems likely that something was messed up in feedings, which cased the ammonia to spike. In a fairly new tank with little bacteria, this can be detrimental. So it's equally likely no parasites were involved at all. There's really no way of knowing if you weren't there to witness the problems.