Hi Shevy,
Only treat when you have to and know what your treating for as there could be a possibility the ones in the QT tank are OK and if they are not showing any signs then leave well alone mate and make sure you do the full cycle of treatments on the pond to the letter,so do not leave the last treatment because they all look good and want to eat you have to go the whole hog mate.
Keep an eye on the tank and before you move the fish do a scrape and see whats what. the only thing i would add is if the fish ion the QT are from the same source that have given you the problems in the pond then there is always the chance that when you move them to the main pond it could trigger of the white spot so be very vigilant when you do move them mate.
As for the dips and leaving them over night

forget it never never treat when you can not be there or see whats going on
