This is because 43 dBm is already a high transmit power so that each user already reached its maximum throughput, which is dependent on the allocated subcarriers per user.
To see the difference, you need to look at the lower transmit power regime (e.g., -20 to 10 dBm). If you select that range, then you will see a gap of exactly 10 dB, which corresponds to the difference in the pathloss.
If you are asking why UE3 and UE4 are stuck at 1.1Mbps, it is because in the standard, the farUE is limited to the CQIs of QPSK, and therefore it is not able to switch to higher CQIs when the SNR is higher. That is why it gets stuck at 1.1Mbps.