My mother had a similar car (2002 Solara) and the brakes felt softer after the OEM pads were replaced with "NAPA Ceramix" pads that were supposed to be an exact match for OEM. That car had no ABS, and that might make the pedal feel different from yours.
I bled the brakes often enough, using Valvoline DOT3/4 fluid.
Also +1 on remembering to adjust the drum brakes manually from time to time. Even cars with the best drum brakes need an occasional adjustment for optimum performance.
EDIT: Also, peel back the wheel cylinder boots and check for fluid within the boot. That means the wheel cylinder is not applying properly, and leads to a soft pedal.
EDIT: Apply the brakes at a complete stop and feel if the pedal leaks. If it does, the master cylinder must be replaced.