I would be surprised if it is the indexing. New cables settle in, sometimes called stretch, and develop slack, almost always causing some kind of shifting problem. This is exactly why the LBS told you to bring them back for adjustment. Don't try to adjust it yourself unless you know what you are doing. Right now it is probably just a matter of taking up the slack. If you start turning things it will take the LBS longer to straighten out.
FWIW,
Raymond