Phd Decision Date Gaps?
Most graduate schools in the U.S. follow a policy that accepted candidates are not required to make a decision until a set date agreed upon by the schools (April 15th, I believe).  This means you can (and should) take as much time to make your decision as you need.  It sounds like you do need to make your decision earlier than that deadline (but it might be worth finding out if the other schools do follow that policy and simply asked you to make a decision earlier), so contacting the other schools is probably a good idea.

Remember, however, you are making a decision that will at the very least directly affect the next four to six years of your life, who you work and collaborate with, future contacts, where you live, and what your future employment prospects are!  So, I'll reiterate: take the time you need, and get as much information as you can if you are up against a hard deadline.