During the DTE2 campaign in the JET tokamak we performed a parameter scan in T and D-T complementing existing pulses in H and D. For the different main ion masses H-modes at fixed plasma current and magnetic field can have the pedestal pressure varying by a factor of 4 and the total pressure changing from betaN = 1.0 to 3.0. Based on this wide data set the pedestal and core isotope mass dependencies are investigated. The pedestal shows a strong mass dependence in the density which influences the core due to the strong coupling between both plasma regions. To understand the key causes for the observed isotope mass dependence in the pedestal it is important to unscramble the interplay between heat and particle transport and the ELM stability. For this purpose we developed a dynamic ELM cycle model with basic transport assumptions and a realistic neutral penetration. This model highlights that a mass dependence in the ELM stability of the ELM transport alone cannot explain the observations. One requires a mass dependence in the ELM stability as well as one in the particle transport. Additionally, heat and particle transport require different mass dependencies. The core confinement time increases with pedestal pressure for all isotope masses due to profile stiffness and electromagnetic turbulence stabilisation. Additional to the general trendwe observe T and D-T plasmas with an improved core confinement time compared to H and D plasmas even for matched pedestal pressures. For T a large part of this improvement can be attributed to the unique pedestal composition of higher densities and lower temperatures than H and D. With reduced turbulence efficiency at lower temperatures more turbulent drive in the form of steeper gradients is required to transport the same amount of heat. This picture is supported by quasilinear flux driven modelling using TGLF-SAT2 within ASTRA. With the experimental boundary condition TGLF-SAT2 predicts the core profiles for gyroBohm heat fluxes > 15, however, overestimates the heat and particle transport closer to the turbulent threshold.