  We report evidence for a reentrant spin glass phase in electron-doped
$\text{EuFe}_2\text{As}_2$ single crystals and first traces of the
superconductivity re-entrance in optics. In the close-to-optimal doped
$\text{Eu}(\text{Fe}_{0.91}\text{Ir}_{0.09})_2\text{As}_2$ and
$\text{Eu}(\text{Fe}_{0.93}\text{Rh}_{0.07})_2\text{As}_2$ samples two magnetic
transitions are observed below the superconducting critical temperature $T_c
\approx 21$~K: the canted $A$-type antiferromagnetic order of the
$\text{Eu}^{2+}$ ions sets in around $17\,\text{K}$; the spin glass behavior
occurs another $2\,\text{K}$ lower in temperature. In addition, strong evidence
for an additional transition is found far below the spin glass temperature. Our
extensive optical and magnetic investigations provide new insight into the
interplay of local magnetism and superconductivity in these systems and
elucidate the effect of the spin-glass phase on the reentrant superconducting
state.
