So my step daughter is 2 & 1/2, has been sick for the past two weeks with high fevers, throwing up…

So my step daughter is 2 & 1/2, has been sick for the past two weeks with high fevers, throwing up once every few days from coughing so hard, & just not acting herself. The doctors say it's just a really bad 'virus'. Around the same time she got sick, my fiance & I started noticing that her breath smelled terrible. normally we brush her teeth with normal bubblegum children's toothpaste two times a day. Well since we've noticed this, we try to have her brush three times a day with our mint toothpaste we use. She loves chewing gun so we have even given her that & mints. It seems like no matter what we do her breath just smells so foul. Have any other moms experienced this before? Could it be caused by something?