A free Neutron decays into a hydrogen atom (Proton, Electron, Electron Neutrino) within 15 minutes. That means that a Down Quark transitions to an Up Quark because 2 Down Quarks + 1 Up Quark is an unstable configuration. (Of course, that implies that all the 95+% mass of a Neutron [and Proton], is TRULY made of "virtual particles.")
So, 2xDown, 1xUp is unstable, even though charge is conserved, yet 2xUp, 1xDown is MORE stable, even though charge is ALSO conserved (with the emission of an Electron)!
PLEASE, and I mean this whole-heartedly, WHY? Clearly, some criteria (mass, charge, etc.) has an implied priority, even though Physicists take Herculean efforts to prove such things are "conserved."