User blog comment:Thailog/Ep. 206 "Bloodlines" discussion/@comment-108.9.39.192-20120603001732/@comment-24.101.61.154-20120603005752

I noticed that too, at first nightwing's voice sounded young but it never bothered me but in this episode it did sound deeper. He is also my favorite member on the show.

I think that would be a reason why Wally retired, it makes sense to me.