Why is my bow not grouping my arrows?

I just got a PSE Brute compound bow a week ago. I got brand new arrows which were the best they had, a brand new peep sight, a new whisker biscuit arrow rest, and I kept my Tru Glo sight from my other bow. I started shooting it and I cannot group. Im pretty sure it isn't me thats not doing it right. The whisker biscuit's whiskers are kind of messed up and unorganized in one spot where the right flap of my arrows have been going through so i cut those off and left the straight ones. Is it the whisker biscuit thats causing the problem?