Your condition sounds like typical junk replacement struts at two years
age;  I would consider that the strut(s) are the cause of noise.  I
would also suggest that there was no real problem with the OE struts
two years ago.  I see and drive these every day and rarely do rear
struts make any noise under 150k miles; even rarer are OE Camry struts
that have leakage or performance issues at any mileage.

You may want to check to see if the shaft nut has backed out or if any
of the three upper mount plate nuts are loose, but it requires lifting
the rear deck board.  If the shaft nut is loose, you can attempt to
tighten it in the car (large gold colored nut, 19mm socket).  If it is
loose, there's a possibility that the keyed strut shaft has spun out of
position of the keyed strut mount, which will require strut removal and
the use of a spring compressor to remedy.

More likely, the Sears'omatic strut has failed just like many junk
struts do in short time.  Other areas to look are the rear control rods
that run perpendicular to vehicle travel - look for looseness in the
articulated end bushings.  Worn out swaybar bushings, though extremely
unlikely, could cause a sort of knocking noise.

Toyota MDT in MO