Are the covers removable? because maybe you could put another layer of fabric between the cushions and the covers, to catch more of the feathers. Of course, my featherbed was like this until I got a better class of featherbed -- not sure if it was the quality of the feathers or of the cloth that differed, though.

I had a down and feather sofa that "shed" a ton of feathers when I first got it. I had purchased through a designer so I called to inquire about it. She examined the sofa to find there were gashes in the inner liner. You might carefully check inside one cushions to see if you have a similar problem. If so, return it to the source from which you got it to be repaired. If that's not possible, I'd take it to an upholsterer which you may need to do regardless.