Stop feeding until you get this corrected. Be sure fish eat all food when you resume. Use Ammolock or similar at any hint of ammonia, change the filter daily, and perhaps up the strength of your pump. There are 2 ways to do a qt: cycled, which uses biofiltration and relies on rock and sponge and other things; and non-cycled, which I prefer, which just keeps the premises scrupulously clean and changes the filter floss daily to rid the tank of any particulate waste whatsoever. If your fish are/is somewhat large for the qt tank a very strong pump is a good idea, since it also contributes oxygen; and you may have to do daily 10% water changes to keep it in check.
The reason I don't trust cycled qts---a) they're not always ready when you need them and b) if not managed expertly (experts are somewhat rare in the newbie forum) they can turn on you and produce bad stuff fast if you lean on them too hard. If you choose cycled, just be careful and test often: there is an ammonia badge from Kent that will warn you ammonia is present. That would be a good thing.