Built in the 50's, I'm going to guess that it is conventional rafter design (vs. trusses). That it is happening only over the car port is your first good clue. I would look at the front and back fascia areas to see if they look pushed out a tiny bit, allowing the ridge to sag. My guess is that they continued the same roof design over the car port that they used on the rest of the house. But, the car port has almost nothing (no front/side/center bearing walls) supporting and holding the rafter system together as the "locked together" unit it is designed to be. Or, maybe that HUGE joist span over the car port is just too long. Look for sagging joists too, which would allow the ridge to sag.
An inspection by a trustworthy builder would reveal the root cause. Since you have no snow load in Florida, and if their are no major structural deficiencies (i.e., cracked ridge board, etc.), it might be just a cosmetic thing. There are sagging roofs that have lasted for centuries.