Agree with above regarding brook. Since the isolation box is basically DT water, it is assumed that all fish in the tank whether in or out the isolation box are infected with brook. I suggest to move all fish to QT and run fallow for 6 weeks to eliminate brook from DT. Meanwhile in QT perform several baths of formalin or acriflavine, (i prefer acriflavine, its safer for both you and the fish), you can also dose the QT with acriflavine for a week or two if you don't want t perform the bath.
Even better, if you don't have corals you can add ruby reef rally directly to tank. (I tried this and its reef safe (all inverts including corals) but corals might suffer because acriflavine dyes the water yellowish color which affect the photosynthetic spectrum of the light and might effect the corals that demand high amount of light like sps, all my corals except one sps frag made it)
Best of luck
