(a) After entering an order establishing child support in accordance with the provisions of section 5-603, the court may from time to time afterward, upon the motion of either of the parties or other proper person having actual or legal custody of the minor child or children of the parties, revise or alter the order concerning the support of the children, and make a new order concerning the same, issuing it forthwith, as the circumstances of the parents or other proper person or persons and the benefit of the children may require.
(b) All orders modifying an award of child support must conform to the provisions regarding child support guidelines that are set forth in article 13 of this chapter.
(c) An order providing for child support payments may be revised or altered for the reason, inter alia, that the existing order provides for child support payments in an amount that is less than eighty-five percent or more than one hundred fifteen percent of the amount that would be required to be paid under the provisions of the child support guidelines that are set forth in article 13 of this chapter.