I'm going through the same with my Wrasse but I haven't been able to catch him to move him to the QT. I set up a trap for two weeks and he never went near it. I've tried catching him when he's laying on the bottom but as soon as I approached he'd swim away. Draining the tank to catch him is not an option, I don't want to stress out the whole tank doing so. Reading through this thread I would be doing the same you have done but it seems to not have any effect which is discouraging. I feel so helpless watching him breathing heavy laying on the sand, all the other fish are doing great and no signs of any ailment.