Definitely ask the local spring place. It's entirely possible the springs need replacement, but it's also entirely possible they're okay. The rear springs on the E-SuperDuty chassis (and I assume some other years of at least the E450 chassis, and maybe other E series chassis) have nearly flat springs by design. I don't see anything obviously wrong in your picture, but I'm also no spring expert, not by a very long shot.
Getting some air in the helper springs will be a good start (and free), and probably coincidentally make the ride a bit better as well. They don't take a lot of air; a bicycle pump is very practical for putting air in if you don't have or don't want to mess with a compressor.