The ball didn't cause it unless it killed that pistil. pistils turn color when they die or get pollinated (they die after pollination).
other reasons -- wind burn, heat or excess light could cause premature pistil death.
Not sure how it effects the ripening of the calyx... if it still ripens as normal it's obvioulsy an insignificant problem. I have had slightly windburned pistils before... those colas still turned out okay... close enough that the naked eye saw no difference.. maybe in an extreme case with more damage it wouldn't be the same?
Look for pollen sacs or nanners... if confident there's no male bits on it, probably environemtally caused.
Neighbors growing weed? If one of them has a herm and you are downwind could cause pollination too.
on a typical 9-week flower timeline, should be turning brown around 6 weeks.. maybe some by 5 weeks. A faster developing pheno might show brown pistils even sooner - for perspective. Lots of genetic variety involved....