Is it possible to develop the inner pecs and the upper pecs at a faster rate than the rest of the pecs? It seems like it wouldn't be, since the muscle contracts as a whole. But this is a weak spot I'd like to address if possible.
Focus on incline pressing for awhile.
You can target the development of this area using exercises such as incline cable flyes and incline dumbbell flyes, as well as standing cable crossovers. When using an incline bench, try to have the incline at or around 30 degrees if possible because anything that is angled 45 degrees or greater activates the shoulders more than the upper pecs.
Get big or die tryin'.
Charlie Cates, CPT