You'll need to treat the Ich. You can do copper with cupramine and a test kit or hyposalinity. Look them up on Google.
I choose hyposalinity.
As for the tank, it will run it's course in 4-6 weeks i believe. Check that against your research. Ich needs a fish host so any free floating parasite in your tank will die out in time since they will not have hosts to feed from.
Expect the process to take an additional month AFTER you have treated and don't see any Ich on the fish. The clock in the QT starts after the fish show no signs of infection.
Read up and get a good idea.
125 gal mixed REEF