Help with hypo and quarantine

[fishrfriends]

Any help greatly appreciated!
I have a 40 gallon tank with two clowns (about 5 weeks) and just added 3 chromis yesterday (2 died, from LFS). I know, stupid, but ...
Just added the Chromis yesterday, and this a.m. one of the clowns has a few white spots - probably ich. Yes, I know, QT - whacking myself over the head. However, what's the best thing now to help?
If I catch it this early can I save the fish from my being stupid?
I don't have a QT, but I have a 10 gallon I mix seawater in for my main tank that I could use.
Should I put all three fish in? Or just the one that has spots?
I don't have the right refractometer - can I start with the swing arm type and gradually bring the salinity down until I get to the store? Obviously, it's not a cycled QT.
WHat would be best? Leave the fish in the main tank and cycle the QT? Or put them in an uncycled QT, and watch the water quality?
I know you guys are probably very frustrated with us newbies and the dumb mistakes we make, but still help would be appreciated ... Thanks!

 

[oceanic110]

All three fish should br QT, and the display tank should be fishless for at least 30 days. I would not use anything else than a refractometer to do Hypo, I think you would be wasting your time with a swing arm.

 

[fishrfriends]

thank you!

 

[beth]

What type tank do you have? If it is strictly FO, meaning no LR or inverts, then you can perform hyposalinity right in the display wo any problem.