Hi Fresca, you can usually tell if your bird is chewing his/her feathers by the state of them, the shaft will look chewed whereas feathers lost in a molt are usually "clean" and normal looking. It does sound by your description of your fid's chest that he is indeed plucking, if this is so you will have to try to work out the reasons why he is doing so. Why not have a word with your avian vet and ask for advice on how to stop this. The problem with feather plucking is that it can become habitual and is often difficult to stop. If he isn't plucking and not replacing feathers then he could possibly have a vitamin deficiency, again your vet is the best person to advise you.
I hope you sort this out and please do let us know the outcome.