Yes, you can complain, but I believe it is really the responsibility of the committee/Treasurer to ensure that all invoices are scrutinised prior to being paid. Expecting the strata manager to do it, is a bad idea in my experience.
We recently had a Sydney water bill increase from $8,000 to $40,000 over one quarter. But after much agitation from me (as Secretary) and panic by the building manager who could not identify a leak anywhere, it was confirmed by Sydney Water that there was a faulty meter (they guessed the usage!). The bill was reduced accordingly.
As Jimmy has said, there could be several reasons for the increased water usage Also, take a walk around the complex and check that there are no obvious leaks, and check the meters as well.
Good luck.