Budgie Always Loosing Down Feathers!

[Bird Woman 0]

I rescued a little yellow budgie from the native mynas 3 months ago, and put her into a spare cage we have. 

She's been kept inside, and is let out to fly around in our sunroom for around 1 hour at the same time every afternoon.

We have been giving her "room mate", a 12 year old Regent Parrot (in his own cage), "Vetafarm essential vitamins + minerals + amino acids" for years, and so have been giving the budgie the same, at the correct dose in her water on 3 days per week.

The budgie seems happy, and is chattering, eating (Trill budgie mix) and drinking normally, BUT continually looses lots of down feathers......like a dozen + every day!

She's not preening excessively, and appears healthy, but is there something wrong, and perish the thought need a cage friend in addition to her room mate?

Many thanks in advance.