Moved Fish

[cow]

Hello, I am certainly feeling down tonight as about a month ago i took my 2 14 yr old goldfish (common) to my friends at a private pet shop, i have to travel and cant care for all the needs and close attention they required. Anyhow before i moved them I would change 2-3 gallons of water from the pet store to my home, after about 2 weeks i moved them to the pet store, both here and there they were put in 20 gallon tanks, good filters etc. One thing different is pet store uses salt where i didnt, My gh was 0 and hers is 180. So once we got them to the pet store, One of them that i had been having trouble with for about 4 months floating at top and sometimes on side, but each morning would swim to eat then float all day at top, started swimming around and sitting at bottom, he did this for the 3 weeks he was there until she called and said he died, the other remaining one didnt have anything wrong that i could see when i had them, but now it is showing signs of swollen body and scales are a bit out she said not sticking out but you can tell the body is swollen, she moved it out of tank with salt and into a 10 gallon no salt, added a tsp of epsom salt, this was two days ago and it is still alive. I feel i might have sent them over the edge with the better water chemistry, mine was from a softener and no gh the pet store used hard water and no softener and added salt 1 tsp per gallon. I guess i just want some opinions, other question is does osmotic shock or stress cause swellling and some bleeding on fins?? The one that died had white scales on tail fin and lower part of back of body, this was not there before, this was surprising to see when i picked it up to bury, why would this have happened?
Thanks

 

[cow]

I am concerned by trying to do better for my fish i might have made it worse, obviously did, the one I mentioned that floated all the time, i want to say i was trying all kinds of foods and a diet of peas for a week in case he had constipation, but he never recovered, I need to know your thoughts on all this if you have any as i feel horrible, I have to go again soon and just want to know what may have gone wrong, or what might have been wrong or going wrong with the one that is still alive but swollen? thanks again

I m searching on here to see if anyone might know why the back end of the goldfish that died turned white then he died, I read it could be ammonia but this was a big area of white, not just spots , it was entire back end toward tail, half way up body?? I am searching to maybe find possible reasons why one left is swelling and has some bleeding on back toward tail?