  Randomly rotating particles that have been isotropically labeled with rigidly
linked fluorophores will undergo non-isotropic (patchy) photobleaching under
illumination due to the dipole coupling of fluorophores with light. For a
rotational diffusion rate $D$ of the particle and a photobleaching timescale
$\tau$ of the fluorophores, the dynamics of this process are characterized by
the dimensionless combination $D \tau$. We find significant interparticle
fluctuations at intermediate $D \tau$. These fluctuations vanish at both large
and small $D \tau$, or at small or large elapsed times $t$. Associated with
these fluctuations between particles, we also observe transient
non-monotonicities of the brightness of individual particles. These
non-monotonicities can be as much 20\% of the original brightness. We show that
these novel photobleach-fluctuations dominate over variability of
single-fluorophore orientation when there are at least $10^3$ fluorophores on
individual particles.
