Nock left is weak, for right handed shooter,I shoot mine to test at 5 yards or so,that should tell you. Also be sure to draw the same when you are testing,it make a huge difference if you draw once at 28 and another at 25. Try to be consistant on draw length. The 75 should hit nock right and as you lighten the spine it should move toward the right.
I usually do this bare shaft until I fine the right one then build the others accordingly.
And yes the way you grip the bow and your release will effect the arrow flight so try when you are testing to do that the same each time then if one flies bad after they are fletched you will know it is in your form,not the set up. you need,at least I need confidenst in the set up to shoot well. Then you know it is you and can work on your form. Hang in ,it will get easier.
Pappy