Wallace, who had submitted his test, received a TKO win.
"These guys are told, months and months in advance, 'get bloods done'," said promoter Steve Alderton.
"It's a shame, but Brendon was well ahead [on the scorecards]."
Whanganui Thai Fighters' Conroy King was not as fortunate against Rotorua's Jake McCowatt, who started with rapid-fire combinations that did damage.
In the second round, King's left eyebrow was cut open and after an inspection by the ringside doctor, the fight was called.
TPK Whanganui's Conrad Gray had a height disadvantage to overcome with New Plymouth's Callum MacBeth, and got a warning after tripping him over a couple of times.
MacBeth settled in the second round and connected when Gray came forward, getting in some big upper cuts.
It was leg kicks vs roundhouse punches in the third round in a massive exchange of blows, with MacBeth pouring it on in the later stages, and, although Gray was still there to the finish, the unanimous decision went against him.
Wanganui Warrior Brayden Maua showed his power early on against Masterton's Matt Gain, with power blows every time an opening appeared.
But Gain was cagey - defending well, getting his shots in and getting quickly out of harm over the next two rounds, with Maua moving backwards to create room but simply unable to get off as many strikes as he needed.
Gain convinced two of the three judges he had done enough to get the decision.