Help! My budgie has mites again?

Hello everyone, I just wanted to ask you.
I have a budgie, and around Christmas I discovered he had probably mites. So I went to the vet and he gave me some medication for it. I think it worked, but it still seems like something is going on.
I don’t know if its lack of vitamins, or the mites came back. I still have the medication, should I treat him again? I am afraid, it is going to hurt him. The vet is closed for few weeks, I don’t know what to do. Please someone help.
Thank you so much, and have a lovely day.