[George]

Can you borrow a bigger tank as your QT? The 29 g is too small for all your fish. It's not the end of the world if the QT is not cycled. I do that all the time. The only thing that you need to manage is ammonia in QT and that is very easy to deal with. Regular water change and prime will manage ammonia problem. An ammonia badge will help with monitoring ammonia level.
Worse comes to worst, I will put all fish in your 29g if no ways to get a bigger tank. Use bare tank don't put any extra in there (no rocks etc). I will monitor ammonia closely and have prepared salt water on hand to do water change. Treat ich in QT with your favor method. Fallow your DT for 8+ weeks. (however there are new strains of ich that last more than 8 weeks without host. Some people propose to fallow for 11+ weeks now)
You should get rid of the ich in your DT. Don't let it run its course. It will come back again as your experience. You may not be lucky in the next wave of attack.