Play between wheels and axle

Hello folks,
I have a 12' GT. Today, I installed some springs. After installing the rears, I put my rear wheels back on the studs to tighten them and noticed that there is play between the wheels and axle. I removed the wheel and held the rotor and moved it back and forth and could feel a slight play (maybe 1mm or less) of play.
The movement is very little, but I've never noticed this before and I'm just wondering if that is something I should have looked at.
Does anything have any knowledge on this issue?

Thanks

Thats normal on a 12 foot mustang. Just kidding! If it's the rotor moving back and forth they're not seating against the axle flanges correctly. Remove them and clean off any rust on the mating surfaces of the rotor and axle flange. But if theres movement when you push pull the studs in and out thats probably normal bearing/gear lash play.

Yea, meant '12.
The rotor does move slightly when I push pull on it. If it is something abnormal, I'm just surprised it would happen on a new car.