If it were my bird, I would treat the whole aviary (assuming vet thinks it is mites.) See if any beaks look odd, scaly mites attack feet and beaks.
I know you're not in US, here are the meds I'd use (or you could ask that expert I sent you to!)
Avian Insect Liquidator - an aviary spray. Spray everywhere, all cracks, nooks, crannies, nests.
SCATT which is moxidectin, on the birdsd day 1 and day 21. It stays in the system 3 weeks. By doing a 2nd dose you are killing all larvae and adults. If you forget the 2nd dose you pretty much have to start over.
Spray AIL again in the environment.