Your response did not answer the questions I asked in my previous post. (?)
If you believe he is over-preening, then it is best you take him to an Avian Vet.
Avian Vets have special training to determine the cause of symptoms resulting from illness or trauma.
This is important as "regular" vets will often overlook symptoms that are quickly obvious to an Avian Vet.
When you rely on anyone who has not had training in Avian diagnosis and care, you may be delaying effective treatment.
This can prolong suffering that may be avoidable.
The bird will often require a more intense, prolonged treatment with a poorer chance of full recovery than it would have if you seek prompt professional diagnosis and treatment at the first sign of illness.
Having your budgie examined by an Avian Vet allows you to develop a good relationship with the vet in case your bird needs care for an injury or illness in the future.
Additionally, it is always helpful for the vet to have a baseline for your bird to refer to should it need future treatment.