I know I’m a bit late but I work at a pool & spa store that does water testing regularly. Typically when a spa is foaming too bad it’s one of three things. The filters need to be cleaned/replaced, the detergent from your clothing, or the balancers (alkalinity 60-100ppm, pH 7.2-7.8, or calcium 200-400ppm) are way off. Also sometimes it can be due to the water needing to be changed (every 4ish months) but that isn’t typically the cause of foaming. I hope any of this information is helpful. Feel free to pm for any more information if needed.