Had a plastic dishwasher line wreck my flooring in the kitchen once.
Another house, had an ice maker line do its thing behind all the appliances for a long time before migrating out to rot the center of the floor
^^^ This ^^^
My first two prime suspects...
Many a water leak has been traced to the above.
And leaking water beneath floor doesn't necessarily always show near the source of leak, either.
Generally speaking, just the main cold water feed into many houses built on slabs is inside concrete slab, then branches out through walls and possibly ceiling to water heater, kitchen / bathroom(s), laundry room, outside hose hydrants.
Best of Luck to you...
