In Washington State, does my employer have to change the 1st Answer to Garnishment after filed with court?

I live in Washington State. My wages are being garnished for a lawsuit I lost. My employer was served with a Writ of Garnishment and they provided the 1st Answer to Garnishment within the 20 day period and it was filed with the court. The garnishment is for $500/paycheck for 60 days. Yesterday, I was released from paying Child Support ($325/paycheck) and my employer is telling me they need to re-file the 1st Answer to the garnishment based on this information. Is that true? I thought once it's filed, it's done and doesn't need to be updated. I'd like the extra $325/paycheck in my pocket instead of going to the garnishment. Thanks for your help.