green parrot falling feathers

i have a green parrot whose feathers are falling i have'nt given him anything except parrot food please tell me what is the problem with him..

add a vitamin to his water dish. also often times parrots should be fed fresh food - the parrot food should just be used as a supplement.

First of all we need to know what the 'green parrot' is. Do you know the species? Can you give us a thorough description or post a photo of the bird.
   
Also the bird could be going through a heavy moult. More information is needed to know what exactly is happening but you should consider taking the bird to an avian vet. If you don't want to, then you should take the bird to someone who who is willing to care for the it & do this. You should not own a parrot & not know what it is or why 'feathers are falling out'.