I bought a used Specialized Hardrock Pro last year and have fallen/banged it on the ground a few times. I've recently noticed that after a little while riding (1-2 miles) the rear wheel is angled toward the left, brake side of the frame, the tire almost rubbing against the chainstay. I usually hop off, undo the quick-release and tighten it a little then squeeze it back. This is making me have to do small RD and brake adjustments each time. The rear disc rotor is a little bent, but very little, maybe 1-2 mm. Is it this or something else? I've been told I have the QR much tighter than needed, could that be it? I don't think it's an issue of cracks or bends in the frame, but I may just be missing it. Thanks in advance.

Robert