Considering it's a quarantine tank it stands to reason the fish were already stressed to begin with. The more you feed them the worse your ammonia problem will be but IMHO changing enough water to eliminate the ammonia will also add to the stress, unless you want to change about a pint every 15 minutes or so. It's an acclimation issue. Get the ammonia under control first then feed often but sparingly, don't leave any uneaten food in the tank. When you change water get it out of your display tank if the chemistry is right, and change 5% every week.
I guess if it were me I'd stop feeding the fish and stop changing water as well. Then run down to the LFS and pick up some
AmQuel+ (you're talking about salt water right?). Follow the directions on the package, drop in an air stone if you have one and keep an eye on the pH. If the LFS only has AmQuel (without the +) then you'd need a buffer as well.
I've never used the stuff but here's what their website has to say about it:
AmQuel functions as well in salt water as it does in fresh water; whereas zeolites do not remove ammonia in salt water
To prevent a pH drop, use either AmQuel Plus Buffers or Pure Dry AmQuel instead of liquid AmQuel.
AmQuel should not be added to water containing active, therapeutic dosages of dyes such as methylene blue, acriflavine, or malachite green
incompatible with the Nessler-type test reagents, resulting in false, high ammonia
test kits using salicylate-type reagents such as Kordon's AquaTru Test Kit #35970 for salt water
are required for accurate test results
AmQuel is non-toxic when used as directed. Numerous species of freshwater and marine fishes, invertebrates and plants have been exposed to AmQuel with no toxic effects.
Hope this helps, keep us posted.
Ted