We present a spectrophotometric analysis of galaxies belonging to the dynamically young, massive cluster RX J0152.7-1357 at z~0.84, aimed at understanding the effects of the cluster environment on the star formation histories of these galaxies. The analysis focuses on the spectral energy distribution (SED) of the galaxies, which is used to derive their physical properties, such as stellar mass, star formation rate, and metallicity. The results show that the cluster environment has a significant impact on the star formation histories of the galaxies, with the most massive galaxies being the most affected. The study provides new insights into the role of the cluster environment in shaping the evolution of galaxies and highlights the importance of considering the environmental effects in the interpretation of galaxy observations.