Mounted tv too high, OK to use same studs to remount?
Absolutely no problem.  

The screws (actually called "lag bolts") bite into the wood immediately around them, and the wood fibers around that hold the bolt in place.

Yes the holes you made already weaken the fibers immediately around them but the amount is insignificant.  And, for a flat screen TV like you're describing, the weight you'll be putting on each bolt is hardly enough for the bolt to notice.