Take a look at last year’s admission rates by GPA at http://talk.collegeconfidential.com/discussion/comment/21182988/#Comment_21182988 . Note that your UC GPA of 4.0 falls into the ~50% admit range of the least selective UCs that you applied to (high matches).
So if your essays and such were not that good in the eyes of admission readers, they could have been the reason for denial at those three UCs.
Really, you should have included UCSC as a match and UCR and UCM as low matches.