Overview of O I, [O I], Fe I, Fe II, C I, and Br-γ lines in B243, B268, B275, and B337. The multiple epochs are overplotted, and the wavelengths are shown above each panel in nm. The [O I] and Fe II lines of B337 are not shown because the bluer part of the X-shooter spectrum is too noisy. All stars display some nebular emission (residuals) on the Br-γ emission (right panel). The variability between the epochs is discussed in Sect. 7.