Damp yellow spots on living room paintwork & faint musty odor?

Hey everyone, hoping to get some advice on a puzzling home maintenance issue. Over the last two weeks, I started noticing some faint yellowish damp stains appearing on the painted plasterboard wall in our living room, right near the baseboards. On top of that, there's this subtle, annoying musty smell in the room that won't go away no matter how long I leave the windows open. I checked behind the furniture and under the floor, but can't see any obvious dripping pipes. I really don't want a plumber who will just start hacking away at my painted walls blindly using outdated trial-and-error methods. I definitely need a specialized water leak detection melbourne company that uses modern non-invasive tools to isolate the exact cause and give me a proper assessment report. Has anyone faced a similar hidden wall leak, and who did you trust to locate it accurately?