  The 100% detection rate of Ly$\alpha$ emission in a sample of four luminous
$z\sim8$ galaxies with red Spitzer/IRAC colors suggests objects with unusual
ionizing capabilities that created early ionized bubbles in a neutral era.
Whether such bubbles reflect enhanced ionizing properties (nature) or an
overdense environment (nurture), however, remains unclear. Here we aim to
distinguish between these hypotheses via a search for Ly$\alpha$ emission in
five fainter galaxies drawn from the CANDELS-GOODS fields using a similar IRAC
excess and UV magnitudes that should reflect reduced clustering effects. Using
Keck/MOSFIRE we tentatively detect $>4\sigma$ line emission in only two targets
at redshifts $z_{\rm Ly\alpha}$=7.1081 and $z_{\rm Ly\alpha}$=7.9622 with
rest-frame EWs of 16-17 A, $\sim$1.5$\times$ weaker compared to their brighter
counterparts. Thus we find a reduced rate for Ly$\alpha$ emission of
$0.40^{+0.30}_{-0.25}$ compared to $1.00^{+0.00}_{-0.44}$ for more luminous
examples. The lower rate agrees with predictions from simulations of a mostly
neutral IGM and an intrinsic EW$_{0,\rm Ly\alpha}$ distribution for $z\sim6$
galaxies. However, even with an extreme EW$_{0,\rm Ly\alpha}$ model, it is
challenging to match the detection rate for the luminous objects. SED-fitting
of our fainter sample indicates young and star-forming systems, albeit with
less extreme SFRs and ionization parameters compared to their luminous
counterparts. The enhanced Ly$\alpha$ rate in luminous galaxies is thus likely
a byproduct of both extreme ionizing properties as well as environment effects.
Further studies with JWST may be required to resolve the physical nature of
this puzzling population.
