Daughters are 23 & 24 years old, and current child support should stop 5/1 & 8/1. Arrears exist, but now deductions have increased. How do I modify?

You would have to file a motion to modify and substantiate a change of of circumstances to reduce the payments. I do not know how long the current order remained unmodified other than for COLA but presumably you had your two sons with you for at least 12 years. But if the deductions are for arrears, then there wouldn't be a change of circumstances since child support can be modified going forward but not for money owed in the past.