You have to use a dacron string with that bow.Your string should be right for that bow.Your nocks shouldn't be too tight on the string.Put the nock on the string,holding the bow horizontal,arrow pointing downward,give the string a tap with your finger-near the nock.The arrow should come off the string.
I adjust them by boiling water in a cup,hold the nock in for 30 seconds to a minute and pry open with a butter knife.Some sand the nock throat till it is right.Too tight a nock will definitely affect arrow flight adversely.Good luck.