Need helping filling out mine and my wifes w-4's

So I am needing helping matching mine and my wifes w-4's to get the best outcome, I have filled them out like every other year and they're not holding out any federal taxes. I updated my wifes which she works full time and on step 4c  put down to hold out an additional $76.92 and that is all they are holding out now...... My status has changed from full time position to Part Time and same thing, put in our 2 dependents, etc... and they are not holding out any federal taxes either. But for both of us they hold state taxes out. I'm so confused, did something change this year or what?