test wrote:
While flushing the toilet earlier this evening, I think 2 other
people in the house turned on the water, which messed up my toilet's
flush. The water went down a lot of slowly than usual.

A toilet will flush (one time) if the water to the house is turned off! Your
problem is not with incoming water, it's with outgoing waste.

The line is clogged. The clog could be within the toilet fixture itself
(such as a hairbrush or the cat), or downstream.