The pattern across fixtures is often more useful than one symptom.
A single slow sink can be local to that fixture. When toilets, tubs, showers or floor drains begin reacting together, the restriction may be in a drainage path those fixtures share.
Examples include a toilet flush causing a tub to gurgle, wastewater appearing at a lower drain while another fixture is used, or several drains becoming slow around the same time. These patterns do not prove a specific defect, but they can help determine where professional evaluation should begin.
Mechanical cleaning may restore flow when material or roots are restricting a line. It does not repair cracks, offsets, failed joints or other structural conditions that may be present.
What information helps?
Note which fixtures are affected, what happens immediately before the symptom, whether another fixture reacts at the same time, and whether the problem has happened before. Those details can help a drain professional choose an appropriate next step without asking you to diagnose the system yourself.