No, not for a while it will take a few days before he shows any real improvement. When you took him out could you tell if the white spots were raised or showing any other signs of being a parasite or pathogen. I'd also encourage you to set up a hospital tank when funds and time allow. Since it's not eating frozen or prepaired foods yet you options are admittedly more limited as far as meds go. If you don't see any improvement in the next two days I'd either give it another dip or if it starts looking any worse dose your tank.
I'd imagine it's had it's issues due to the stresses involved in collection from the wild. I wouldn't imagine that any chemicals were used in it's capture due to the fish's normal habit of remaining in one spot normally. There is a decent chance that issue may resolve it's self but, this was a fairly expensive fish and you want to keep it in good health. I totally understand Liz!
Best of luck
and
hth