That's normal on cheaper strings. PSE doesn't use the best strings as it is an inexpensive bow. Higher quality strings will fray less, and you will see this on almost every bow and crossbow. The better the strings, the less they fray. I have noticed that my Quest G5 bow's strings are much better than the PSE Brute X.
Personally, given that wax is cheap, I wax all strings and cables after every shoot. If you wait for fraying, it's a lot harder to stop.
Note also that a higher draw weight will contribute to reduced string life.