I'm generally unimpressed with the performance of a 4" carbon filter. It's better than no filter at all but both my kids have said, "Dad, your house smells like weed." And that was before I put a bonsai mother in my living room as a decorative plant. I grow in a bedroom closet and it's not unpleasant. In fact, it's kinda nice. As long as my clothes don't smell like weed when I go to the office, It's all good. And yeah, i keep my clothes in a separate closet.
2 filters would definitely help. 2 filters = more contact area and more contact time between the fluid (in this case air) and the filter media.