flukes???

I currently have three chinese weatherfish (almost identical to the
weather loach) in quarantine. I've had one for four weeks and two for a
week and a half and they are being isolated before adding to the main
tank.

One of them is not as active as the others and until recently has only
eaten if hand-fed. Its breathing has occasionally been very rapid, for
no visible reason and it likes to hide or hang out on the top of the
filter (fluval 1+). I have been making sure it does eat a little and
doing 30% water changes every 3 days and it seems to be less lethargic
and more interested in food.

No visible signs of disease, no ammonia, no nitrites and I don't have a
nitrate kit at the moment, but as the other two fish are fine I'm not
inclined to suspect water quality.

might this be parasites? - specifically flukes? If so... would either of
the two followwing ideas be any good?

1) salt dip all fish, transfer to bucket of nice clean water, leave them
there for 30 mins to an hour while I fill the tank with a salt dip[
solution and run the filter, then fill tank with clean water (having
rinsed the filter medium well in dechlorinated water) and return fish.

2) don't do this yet, but if fish continues to improve, immediately dip
all of them before adding to the main tank.

Is method two risky or not? are the eggs on the fish or in the water?

Am I unduly paranoid?

help!
--
sophie