@zzing Have a read of:
https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans

You have set Fan 0 and Fan 1 up as thermostatically controlled fan for Heater 1 and heater 2 (so far so good). This means they will cool those extruder heatsinks from 75C and higher in your config.

You have then setup tool 0 and tool 1 to use fan 0 and fan 1 as the part cooling fans, really they should (presumably) both use fan 2?