they seem to me to be commonplace markings of rotors with 29K miles if the marks circle around disc.

by radial do you mean circular around disc or radiating form center outward?

do you see these marks on the front rotors.

before you go any further, do the basics and tighten everything up in the rear; spare wheel, jack, tool kit, battery - in rear or under seat.

spec the torque on the wheel lug nuts.

btw, there is still a bit of debate about cold water on hot discs, steady stream of cool water for example