Does the child placement formula apply?

I am father with joint custody and secondary placement of my one-year-old daughter. Her mother and I currently split time with the mom having four overnights a week and I three every week, however it's an agreement she and I have and it's not legally binding. In our initial child support hearing, the court commissioner bypassed the percentage index guidelines because of my income and instead allowed her mom and I to come to an agreement on an acceptable amount per month. Since then however, the mom's income flow isn’t quite as stable and she recently has had to purchase a new car that she isn’t able to afford. If she were to attempt to modify our current order to supplement her added monthly expense, is it probable that our current schedule agreement would be considered in a decision to raise support? In addition to support, I pay half the daycare expenses and I pay for our daughters' health insurance.