Why are our toilets not flushing correctly after our septic system was cleaned?
As a retired country plumber, I would advise against suction or pressure systems.  They are a no- no in older septic tank installations particularly ones using salt glaze fire clay pipes with cemented joints.  Such pipes are very liable to collapse or obstructions produced by fillets of loose cement that clog up the free flow of the flush. Stick to conventional drain rods and muscle.