So I parked the car went around to the other side, and noticed the back of the car on the right side is sitting about an inch to two inches lower than the left rear. I took a quick look underneath and my control arms and springs look identical except it looks from underneath like someone is leaning on the car. broken spring? because it looks normal. can one spring sag faster than the other?

Thanks.

A lot of things can cause this including extra weight in trunk, broken spring mount or shock. Strut out of adjustment etc.
You gotta get under there and check everything out. How does the camber look.

From the rust problem you have it could be that also. I agree you need to get under there and check it out.