Normally, the type of wear pattern that you describe is characteristic of under-inflated tires, but since you are running 37 psi in them, it doesn't sound like they are underinflated. Then again, what is the vehicle manufacturer's recommendation regarding inflation pressure?
You have not told us the type of vehicle this is, and whether it has independent rear suspension or a solid rear axle, so please post back with that information.
In the absence of other information, it sounds like your tires are underinflated, so I am going to advance the possibility that your tire gauge is not accurate.
Also--I have never heard of anyone being able to detect tire wear after just 700 miles. Is it possible that you meant to indicate 7,000 miles?
We really need more information from you.