If you have a rock from your DT that you can keep in the QT tank and fill the tank as much as possible from DT then add bacteria to the QT, move the fish like yesterday and treat with ich treatment. Feed well.... in addition to a ich treatment use Paragard. Paraguard is like a general overall medicine. Helps with bacteria, fluke, ich.... you dose a little every day and does not accumulate day to day. You want someplace for the fish to hide. Bare bottom with 2 inch PVC is good. The rock will have bacteria on it. Add airstone. Test for ammonia and if it elevates them manage with water changes and continue to use the bacteria additive as needed. It actually will quickly reduce ammonia. When I cycled using the product ammonia peeked at 1 ppm. Then went down. But your using a good portion of DT water and a rock so you should be good to go. The ich treatment I used is attached. I do have a copper based ich treatment but did not need to use it. Copper is more toxic to fish. But can be very effective.