Left: HRD for the 16 targets with stellar parameters determined from the G230LB STIS spectra, shown as blue stars. The blue point shows the typical uncertainties on the stellar parameters (see Section 3.1 for more details and caveats). The grey lines show SMC stellar tracks using a mass-dependent overshooting parameter (Schootemeijer et al. 2019; Hastings et al. 2021), where dashes are marked at intervals of 0.05 Myr. The dashed lines show isochrones of ages 10, 20, and 30 Myr. Spectral types for SMC dwarf stars are shown using the calibration presented in Shenar et al. (2024). Large black circles mark the stars labelled ‘embedded’ in Table 3. Right: Same as the left panel but we add the stellar parameters determined from Patrick et al. (2022) in red. The uncertainties are illustrated with the red point. Black lines connect the stellar parameters derived using the two methods.