The ability to capture the isotope mass scaling of core confinement seen in experiment is validated with JETTO-TGLF for low power JET-ILW discharges across H, D and T. The cases analysed include Ohmic discharges spanning the linear and saturated Ohmic confinement regimes as well as a trio of L-modes. The TGLF saturation rules SAT1–SAT3 are seen to predict a similar isotope scaling across both the ITG- and TEM-dominated discharges simulated, despite for the latter case the inclusion of the TEM branch of SAT3. The models demonstrate good agreement with experiment for the scaling between D and T plasmas, however a discrepancy is observed for H in the ITG-dominated discharges of higher density, as well as a systematic overprediction of the confinement time on the order of 20% in most cases. A retuned version of the SAT3 model, which was fit to better recreate fluxes close to the transport threshold, is seen to improve the magnitude of confinement predictions across all shots owing to an increased transport stiffness. This retuning was not seen to influence the confinement isotope scaling however, and possible transport mechanisms responsible for the continued discrepancy of higher density Ohmic and L-mode discharges in H are discussed.