Your bird is either stressed about something or that it is bored. Has his cage been moved or has someone that was important to the bird left? Since you went on vacation that is the main reason. The parrot felt left out and forgotten.

When was the last time that he was taken out of the cage, or played with? Birds need a lot of attention and when they don't get it they tend to pull out there feathers. If this is the first time that this has happened then there is still hope. But if this continues your bird will be bald and the feathers wont grow back.You could also try buying new toys for him.

By them continuing to pull out the feathers it hurts the follicles which wont produce the feathers anymore.
I would start taking him out of the cage more and spending more time with you. Let him sit on the kitchen chair while you are doing something in the kitchen, or sitting with you while you are watching tv.

Foods I suggest
The Fresh Food Mix: Always ensure 1 fruit and vegetable has a high vitamin A content in it (papaya, sweet potatoes, pumpkin). Vitamin A aids in Calcium absorption. Offering 5 or 6 fruits and 5 or 6 vegetables daily. Several leafy green vegetables which have a high Calcium content (either Swiss Chard, Mustard Greens, etc) are always mandatory in the mix.

Fresh Fruit: Apples (cored), Papaya , Mango (pitted), Oranges (seeded), Cantaloupe, Melon , Star fruit, Pineapple, Pomegranate, Berries (Strawberries, Raspberries, Blackberries, Blueberries), Pears (cored), Peaches (pitted), Plums (pitted), Kiwi (peeled), Banana (peeled), Cherries (pitted), Cranberries, Grapes (with seeds), Grapefruit (seeded), Tangerines (seeded), Cactus Pear (peeled), Banana (peeled) - Note Banana is only served fresh.

Good Luck