Wondering if struts are bad?

The other day as I was cleaning out my trunk I noticed as I put pressure on the trunk that the car dipped down. So I was started pushing down on the rear of the car and noticed that it didn't seem to take much effort to get the car to push down a little bit. However when pushing down hard and letting go there was no bounce at all to the car. Can't imagine the struts would be bad already. Just bought the car 6 months ago as a GM Certified Used Car. Last time I was at the shop for the 27 point inspection they didn't say anything about the struts being bad. So I just wanted to make sure everything was fine.