Sorry, but it isn't that simple. Parrots have needs more complex than just what vitamins they intake. I've had my parrot for 5 years and he started plucking when I first got him. I took the advice of folks on the Grey forum and threw all their suggestions at him and he hasn't plucked since. Here are the things I did.
Hung a telephone book inside his cage to give him something to shred.
Hung a full-spectrum light above his cage so his full vision functions can be exercised (like a human living in a cave, a parrot living without full-spectrum light is depressed). This doesn't have to be expensive, just a flourescent light unit which you can get for less than $20 and a full-spectrum bulb to install in it.
Began feeding him a breakfast of "glop" which consists of the following recipe: 3 slices whole grain low-sodium toast, 1/2 tsp flax seed oil, 2 tsp red palm oil, stage 2 organic baby food of high-content vitamin A (such as sweet potatoes, carrots, etc:), 2 tbsp ogranic yogurt and a chopped-up high-content vitamin A vegtable such as kale. Mix all together, divide into 10 or so portions, freeze and thaw as used. ( I freeze in 2-portion baggies as two days seems to be the max frig time on this stuff).
Feed him whatever I'm eating for dinner keeping in mind that some human foods are poison to him (such as mushrooms, fruit seeds, avacado, and a few other things. Google "parrot diet" to get a full list of no-nos)
Keep parrot nugget and seed mixtures in his cage for "on demand" feeding. And plenty of clean water of course.
Spend a little time each day cuddling him. Remember these guys have the emotional needs and maturity of a 2-year old child, they need physical and emotional contact with their "flock" (that's you).
I hope this helps. Good luck to you and your bird.