re: Slab leak detection - plumber recommendation?

I’m a little concerned that it’s from something like this. I have one downspout that’s close but goes to a French drain. I’ve got an irrigation system pretty close. But the wet and rotten spots don’t necessarily correspond. There is a straight line across the house where it was clearly wet. It makes a 90 at one point.

I’m wondering about drain and sewer lines that wouldn’t show up on a meter or pressure test. I’m hoping a plumber can find something like that.

I’ve used American leak detection 3 times (2 for my pool). Only one of the technicians seemed like he knew what he was doing and he accurately found the leak in my pool. The other two guys seemed amateurish. I’m hoping a good plumber can help