It's always a fine line with younger players in terms of ball security. You have to balance getting reps and experience with putting the team in a hole, and also have to be careful not to overreact and damage their self-esteem.
That said, I also think it's important to recognize that not every turnover is the same. On replay, IKM's turnover was not the result of poor ball security, but rather was a perfect helmet-on-ball hit, and probably would have happened to a veteran RB as well. Smith's and ISM's turnovers appeared more careless. I remember saying out loud after IKM's turnover, that I hope Kirk goes right back to him and doesn't put him in the doghouse.
It's also important to mention that the reluctance to use the younger running backs more may not have anything to do with turnover risk. I strongly suspect that reading blitzes and pass-pro are bigger concerns on the part of the coaches.