Always salt, yes, and quarantine for at least 2 weeks
You can choose yourself what you do with the Melafix and Pimafix, but I wouldn't add anything unless I'd see some rips in the fins or something
Stress zyme is a kind of conditioner, you can use that if you want to. And no, it's not needed to double the dose of conditioner unless it will say on the bottle somewhere that new fish will benefit from higher dosage

I didn't get a new fish today.  Went to Petsmart to get my free fish, and their fish didn't look well.  I didn't even need a magnifying glass to see the spots on the fishes tails.  One was dead, floating by the filter.  They were really busy today, so I didn't wait around to talk to them.  Poor fishes 

I bought all my big beautiful orandas from petsmart and they are all healthy!
It's funny I went to petsmart today and saw another beautiful oranda.  It had a sore tho under her chin so I went and asked if I bought her and treated her at home if she would still be under the warranty of two weeks, in case she died.  They said they will treat her in a hospital tank in the back and that they will call me when she is well, in about a week, they said they would never let a customer buy a sick fish intentionally.  They are putting a sign on the tank with my name and phone#.  So I don't know, I've had the best of luck with petsmart and have always got healthy fish from there.  Maybe I've just been lucky.  
So, if Blossom (already named her) is healthy in a week I will be bringing home a new baby!  I asked what they treat with and they said quick cure.  I said do you sell it here and they said no!  They just treat their sick fish with it.  I found that a bit strange that they would treat their fish with something they don't sell in their stores!  BUT I have heard good things about quick cure!

Mindemae, keep fingers crossed for your Blossom

Yeah, that is true Hanna.  When I go to Pet Smart I always ask the employee working if they have a fish tank with fish at home.
What kind of fish do they have, are they familiar with what to use to treat this and that.
If they do not have a fish tank I don't bother asking anymore questions.  I say "Get me a person who is experienced with fish keeping".   Sometimes they have to get the manager for me.  There is always a manager on duty while the store is open.

Awww thanx Hanna, you are so sweet.  I hope Blossom gets well and I can bring her home, I'm keeping my fingers crossed too.

Ya, there was that shop here where I asked them to put salt in the tank with the separated fish for me, but they said they don't do that to their fish there d: And there it's a warranty of like... was it one or two days at most?! I don't want to go there again unless they have another lovely oranda for me

Can't wait to see pictures of her later! She sounds so cute