  We study medium modifications of the dilepton mass spectrum in coherent
photo- and electroproduction of the Rho(1S)- and Rhoprim(2S)-meson resonances
on nuclear targets. The analysis is performed within the coupled Rho,
Rhoprim... channel formalism in which nuclear modifications derive from the
off-diagonal rescatterings. We find that the effect of off-diagonal
rescatterings on the shape of the dilepton mass spectrum in the Rho(1S)-meson
mass region is only marginal but is very important in the Rhoprim mass region.
The main off-diagonal contribution in the Rhoprim mass region comes from the
sequential mechanism gamma* -> Rho -> Rhoprim(2S), which dominates the
Rhoprim(2S) production for heavy nuclei.
  Our results show also that in the Rhoprim(2S) mass region there is a
considerable effect of the interference of the Breit-Wigner tail of
Rho(1S)-meson with the Rhoprim-meson.

High Energy Physics - Phenomenology