I'm curious as to what you would do.
I am fairly clueless regarding Xs and Os on football. But, here goes anyway:
I would trust the program I have built, and the process the program follows. I may give some "new" players a chance to play more and make an impact. I would try to figure out if there are schemes/plays that just aren't working and replace those with schemes/plays that are working - as much as possible.
That's it for in-season changes.