I"m not suggesting they turn to panicked decisions, just pondering those that may help squeeze an extra win or two out of the last two months. I agree that Turner can still be considered a good SS, and that we can't know for certain that Stott would be a better one this season (or just in July and August), but I don't think the argument you presented regarding the respective players' WAR this season makes a case against it.
It's also not about how many games they won in July as it is a playoff race that has five teams locked within half a game of each other coming down the stretch of a playoff race for three WC spots - not to mention a surging Cubs club three back and buying, and the to-this-point underperforming Pads still a part of things as well, 4.5 back.
You're right in that the players just need to play better, but there are slight adjustments that can be considered to do this whether or not better/different-handed players are acquired to support them.