  We examine the nuclear spin-lattice relaxation rates $1/T_1$ of PuRhGa$_5$
and PuCoGa$_5$, both in the superconducting and normal states, as well as their
Knight shifts. Results for both compounds are consistent with a superconducting
gap of d-wave symmetry in the presence of strong impurity scattering, though
with quite different gap-over-$T_c$ ratios $2 \Delta_{0}/ k_B T_c$ (8 for
PuCoGa$_5$ and 5 for PuRhGa$_5$). In the normal state, PuRhGa$_5$ exhibits a
gradual suppression of $(T_1 T)^{-1}$ below 25 K, while measurements for
PuCoGa$_5$ reveal a monotonic increase down to $T_c$. We propose that this
behavior is consistently understood by the crossover from the two-dimensional
quantum antiferromagnetic regime of the local $5f$-electron spins of Pu to the
concomitant formation of the fermion pseudogap based on the two-component
spin-fermion model.
