Your RBs/WRs are similar to mine (RBs Arian Foster, Jahvid Best, Pierre Thomas, Matt Forte; WRs Andre Johnson, Mike Williams TB, Percy Harvin, D. Johnson)
Having said that, have you tried trading one of your RBs for an upgrade at WR?
If your against that, I'd look at San Diego's Malcom Floyd. It sounds like V. Jax is going to be sidelined another 4 weeks (if not longer). Im not much of a Cribbs fan, I guess Id drop him, even though he is good on the returns.