I think my fish has flukes

Question
I had about 130 fry, all new-born & a couple days apart from each other, from various mothers-guppies and platys.  They are in a 3 gallon bow-front tank with a filter that has carbon but also a spinning wheel.  I normally use Whisper but my sister got this for me about a month ago b/c she says it works better.  But I noticed that all of a sudden, their tails started to clamp, and within a couple of days, became pin-tails.  I always change about 10-15% of the water each day, and have raised fry successfully before so this has got me stumped.  I'm down to about 30 in only 2 weeks.

And I was stupid because I had fed some of fry to some of the fish my main tank.  I did noticed one fish, male Twin Bar platy, flicking itself against the bottom of the tank twice.  But then he stopped after I added a little more salt, total about 6 teaspoons for my 5 gallon bow-front tank and raised the temperature.
Two days ago, a different fish, female guppy, started to swim at the surface and occasionally gasping for air.  But when it was feeding time, she was eating and swimming normally again.  Next morning, she's at the surface constantly gasping for air and her gills were inflamed.  She did not eat at all and I looked up her condition online and came across gill flukes.  Unfortunately I had an important appt that day and couldn't come back until night time.  I came across many websites suggesting Had-A-Snail so I bought some, but by then she had already died.

So will the rest of my fish gets gill flukes too?  And from the research I've done online, I think they might have been transferred from my fry who might have had body flukes.

I am trying to find a store locally that carries Life Bearer since I've read that it is safe for fry also.  Do you know what's happening to my fish and also have any suggestions?  I'm sorry the post was so long, but I really do care for these fish.  Oh and btw, I have kept guppies before in the past and have always been successful, and this is my first time keeping platys but I've had them since June 2nd of this year.

Answer
Its probably not gill flukes at all... it is probably an elevated water chemistry issue.  I would get the water chemistry tested in your tanks.  The reason I think it is a water chemistry issue is this:  1) your fry developed clamped tail/fins and died, 2) you are losing fish that are gasping for air.  Inflamed gills can be caused by a few things one of which is a toxic tank.  Your water volume is too small for all of those fish.  With the constant water changes you have probably depleted your bacterial colonies to the point that they can not keep up with waste in the tank.  I also think you have too much salt in the water...  I would try a 50% water change and then have your water tested... when you change the water I would skip the salt for this time and then add it in only for the new water volume every other time.  keep  me posted... dave