The Tigers slumped to their first loss in nine games after Wednesday goals from Reda Johnson and Michail Antonio came either side of Eldin Jakupovic's own goal.
But Bruce, who saw his side level at 1-1 through Robert Koren's header, felt Wednesday's first was offside.
"We probably made more mistakes in 90 minutes than we have in the past three months," he said.
"There were some crazy decisions by the officials. The linesmen and referee arguably had as bad a night as we had. For their first goal, Llera was a yard offside.
"But overall I can't complain because we've made elementary mistakes. We made far too many mistakes in terms of possession.
"We've made mistakes for all of the goals really, and we've been punished. It was a frustrating evening.
"We've been on a hell of a good run but we've got our backsides kicked . We'll have to bounce back."
In conceding Wednesday's second goal, Jakupovic sustained a facial injury that led to 14 minutes of stoppage time.
"He's gone to hospital and we hope he's okay," Bruce said. "We won't know how he is until he's had a scan.
"We might have to use an emergency loan to bring in a goalkeeper."
- Sports & Recreation
- Michail Antonio
- Robert Koren