Read brakes

Have a 2003 Dakota 2wd. Brakes have been getting little soft. Did rears about 30,000 miles ago, replaced rotors and emergency shoes. Took off rear wheels to day to inspect and doesn't look like either side has been working. Pads don't seem worn down at all and rotors are pretty rusty and pitted. Truck sat over this past winter outside, I live in New England. Could calipers on both sides both be stuck or bad proportion valve. Would really appreciate some opinions here as I hate throwing parts at a problem....