In this context, we recall the spectral fine structure at the exciton energy ubiquitous to Ruddlesden-Popper metal halides with a characteristic energy spacing of 35-40 meV (see numerous references in Ref. 17). We had hypothesised, based on a series of experimental observations, that the resonances observed in this fine structure correspond to distinct exciton polaron states with different binding energies and effective masses . We concluded that two of the observed excitonic resonances, labelled X A and X B , are dressed by distinct lattice modes . Specifically, X A is dressed predominantly by M2, while X B had additional dressing from M4 and M6, which are the higher-energy modes at 5.22 and 5.75 meV. Note that these higher-energy modes exhibit large anharmonicities similar to that of M2, as evident in their comparable dynamics to that of M2 at higher temperatures, Fig. . Intriguingly, M1 does not contribute significantly to the exciton polaron while it has much larger contribution to the carrier polaron.