little more clear now...I was thinking you didn't have any really flying good.
I would imagine those few are messed up in one way or another. Maybe you tore some fletching or they are a little bent. Hang the fletching off of a flat surface and roll the arrow to see if it's straight, or spin it with the point on your palm and watch the knock. Lots of ways to check for straight.
It could be a bunch of things, I've even had glue fro mthe inserts break of inside the shaft and mess up arrow flight. When I get an arrow that I know is a flyer I stop shooting it.
One other thing...do you have the same tips on all of your arrows? I did this just the other day, had 3 arrows not shooting the same and couldn't figure out why, the rest were pretty good. Then I realized I had different field points in those three arrows.