Top: Median reconstructed spectral trends as a function of the s₂ light curve decline rate based on our PCA analysis. The four sets of spectra correspond to the four investigated epochs. The color of the individual spectra shows the s₂ light curve decline rate for which they were calculated. Bottom: Subgroup spectra. The gray spectra show those of the subgroup objects (defined by Fig. 5, the blue spectra show their median for each epoch. The red dashed spectrum shows the reconstructed spectrum for s = 2.5 [mag/100 d] (which is the darkest red spectrum on the left-hand side plot), while the black curve shows the spectra of SN 2023ixf.