Id say humidtity was too low.
Might I ask why your humidity is 60 to 70% at all times? That's a little high for Balls if I remember correctly.
With my Bloods, I just watch em.
Then the day before they should shed, I just DRENCH the cage and I've gotten perfect sheds every time.
Might try that.
Also, I dont have ANYTHING rough in my cages. Matter of fact, just Kraft Paper and a water bowl, still perfect sheds.