Hi,
This is just me, but I would:

Pull back the batts locally, and check for any air leak paths from living area to attic -- things like wire or plumbing penetrations, light fixtures, ...
Sometimes you can spot these by the dark stains visible on the FG batts -- this is dust in the air being filtered out by the FG.

Then I would blow cellulose over the batts.
The cellulose will add R value, and (probably more importantly) will stop the convection currents that form in FG and cut its R value under cold conditions. It will also provide some additional resistance to air infiltration.

Another option might be to take the batts out altogether (maybe use them elsewhere), seal up the leaks as above, and then blow in cellulose to the R value you want.

Unless you see evidence of moisture problems up in the attic, I would not try the vapor barrier.

Gary