They are probably overcooked. Pork stays tender and juicy when cooked to an internal temperature of 145 degrees. Lean pork that's cooked to a temperature higher than 155 degrees or so is likely to dry out. It's also critical that you let pork chops rest after cooking. Resting allows the juices to redistribute and settle throughout the meat. If you cut into it right away, the juices will run out all over the plate.