The schematic for the carrier board shows that there are pull-down resistors attached to the gates of the MOSFET drivers of both relays.
This should prevent the behaviour you describe, so I wonder if you are using the relays incorrectly? For example attaching the pumps to the Normally Closed (NC) contact instead of the Normally Open (NO) contact? See page 12 of the data sheet.
Certainly your proposal to change the library code to fix this a) won't work; b) would have unwanted side effects; c) is entirely the wrong approach!