The two models allow the variability amplitude to change between the $3.6~\mu$m and $4.5~\mu$m light curves, but keep the period constant over both observations. The phase shift model includes an additional phase shift parameter for the $3.6~\mu$m data. The BIC is particularly useful in this case since it will penalise the phase shift model for having an additional parameter. For , we calculated $\Delta \mathrm{BIC} = \mathrm{BIC}_{\mathrm{sin}} - \mathrm{BIC}_{\mathrm{phase shift}} = -25$, i.e. the sinusoidal model without a phase shift is strongly favored. For , we find $\Delta \mathrm{BIC} = \mathrm{BIC}_{\mathrm{sin}} - \mathrm{BIC}_{\mathrm{phase shift}} = 5$. In this case the model that includes a phase shift between the light curves is positively favored, but this is not a significant result. We conclude that neither nor show a significant phase shift between their $3.6~\mu$m and $4.5~\mu$m light curves. ]{}\

Comparison with Near-IR Variability Detections
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We previously detected variability in all three targets in our ground-based, $J$-band survey for variability in low-gravity brown dwarfs [@Vos2019]. Ground-based photometric monitoring is an excellent method for detecting variable objects in the near-IR, but due to shorter observation windows and weather constraints, space-based monitoring with *Spitzer* is more effective at measuring rotation periods, particularly for 