Hello @BJHSartorius
first of all for your setup there is no need for a PaHub as all four I2C units have different I2C addresses and therefore all four units can be connected in parallel using these. You can read about I2C here.
I2C addresses of your four units: NCIR: 0x5A; Weight I2C: 0x26; Tof4m: 0x29; ENV III: 0x44/0x70
That said, I don't know why there is an issue when ToF4m is added.
However, I do know why there is an issue with PaHub and ENV III. They both share the same I2C address (0x70). In other words PaHub and ENV III can never be used on the same I2C bus unless you manually (soldering required) change the I2C address of the PaHub; see here.
Thanks
Felix