'03 Sonata Braking Issue

After recently borrowing my mother's 2003 Sonata, I noticed the braking to be, what I would consider, very poor. The pedal goes fairly low and feels mushy, and it seemed to take excessive effort to stop the
vehicle. The car has 25,000 miles on it, and with an older woman driving it, I thought it might need pads. Upon inspection, the pads have between 3/16" and 1/4" remaining. The car has 4-wheel disc brakes. I took the car for a test, and noted that pumping the pedal seems to have little to no effect. Pedal feels soft and spongy, to me. With the car parked, I noted that the pedal would go low, but seemed to hold with my foot on it. The reservoir level is very close to the full mark. The brakes have always made a slight grinding noise, but she was told that that was because it had ceramic pads.
I believe that the car has a 5 yr / 60,000 mile warranty. I was just going to go ahead and replace the front pads while I had the wheels off, but don't want to cause any warranty issue. Would I be right in that anything involving the brakes, other than pads, should be covered under the warranty?? I'd like to have as much info as possible, before I take it to the dealer's.
Thanks
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If it's about four years old and only has 25k, I'd suspect the issue may be rust on the rotors. Take it out somewhere safe and make some stops really slamming the brakes on, almost hard enough to make the car skid or the ABS engage, but not quite. That usually rubs the surface rust off the rotors.
It's also likely that the rust is the cause of the grinding noise. Unfortunately, rust on rotors is specifically not covered by the warranty.
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