Goals from Matt Rhead, Kegan Everington and Alan Power condemned the Blues to a second successive 3-2 reverse, with efforts from Jordan Chapell and Ross Hannah proving in vain.
"I think there is a lot of personnel at the minute who are off their game," said Burr.
"We're doing the best with what we have got at the minute but I think that with one or two the confidence just seems to have drained out of them. But the goals we have conceded have been poor. But we have just got to keep working at it."