It’s a QF lounge. It’s Australian culture NOT to tip. Oz wages are sufficient so staff make a living wage without the need for tips to supplement. Of course staff like tips but its not a critical part of the wage structure.
Well, not to quibble too much, but it is lounge in the USA, where Oz culture to the staff is foreign to most of them. But as a general rule the USA Premium airport lounges do not expect staff to be tipped.