On my list of most common college applicant mistakes, the following would be
#15: Being too rounded to the point of being scattered. It is good to try different things, but at some point you need to pick one or two activities that you care about enough to work at and get good at doing. No one is good at everything, but most are good at something.
#14: Not being well-rounded. Many people have difficulty defining what it means to be “well-rounded.” If all you do is study, you will find adjusting to college difficult because there are so many temptations and distractions. No college wants to accept someone who may flunk out, not graduate, and not become a success story (a.k.a. a potential donor). Demonstrating that you take your studies seriously is very important, but proving that you can maintain good grades and work and do sports or drama or music or something else with equal passion and excel means more and will set you apart from the pack.
However, if you plan to go to a specialty school, they may set a higher priority on your demonstration of skill than on balancing multiple pursuits. Just keep in mind that if you get in based on a single skill, like music or athletics, and anything interferes with your ability to perform, you may not be able to stick around to graduate (because you may lose your scholarship).