07 vert. rear quarter panels retain water after a storm. on 2007 Ford Mustang

My 07 vert isretaining water in the rear quarter panels. you can hear the water when you turn a corner. interior of the car is dry. the water eventually drains out.this never happened the first 3 years that I owned the car. Why is it retaining water now?

Asked by for the 2007 Ford Mustang
It could be that the drains are partially clogged in some way, causing very slow draining.