The other good news is that washing machine water is considered "grey water" and can actually be let to bypass a septic system and be let out on the ground. And the phosphates make for a pretty good fertilizer without harming anything. From what I have heard the washing machine dumps so many gallons of water into the system at once that it is the way to determine if there are more serious problems with a septic system right around the corner. You might want to call in the professionals since the remedy that has been working for you failed this time. Good luck with it.
Check GA law before you do this. In FL, it is illegal to run gray water on the ground, although rarely enforced without a complaint from a neighbor. I have heard that FL is considering changing this law, but for now, keep the washing machines connected to the septic in FL.
Glad to hear that your "mistake" corrected the problem! Old drainfield lines fail over time. May be time for a repair soon...
(And they call me Noithall...)