clothing is covered under the child support, generally speaking:
"What does child support cover?
The term "child support" covers all the economic necessities of life required by a child. These necessities include, but are not limited to, food, clothing, shelter, education, medical care, and other day-to-day expenses."
Tuition is up for grabs, you've already set a precedent for paying for it so if she takes you to court, the judge may order you to continue.
I would keep it out of the court. Next time you get a raise, have your employer withhold the max on your paycheck which means you're paying her 25% of your net check. You'll get the money back when you file your taxes. Consider it forced savings.
The 25% you're paying is the same rate that the court would charge you with BUT...here's the difference. You're paying her 25% of your net right? But you control your net meaning you can tell your employer to take out the IRS rate for withholding or you can increase the amount withheld to as much as you need...then your Ex gets 25% of that amount...right?
The courts would figure your 25% differently on the net. What the courts would do is assign an income tax amount based on their guidelines so chances are, the tax amount according to the court would be less of deduction than you're doing on your paycheck or your get for your taxes so you'll wind up paying her more in child support.