The manual describes how to use vinegar to clean the cells. Once cleaned, you should lower your ph down to 7.2-7.4 and keep it down there to prevent the scale from reoccurring (keep it down there until you TA lowers some, which will happen do to regularly adding acid to lower ph). We recommend Muriatic acid to lower ph.
Also, you cya level of 30 ppm is low for running a swg. See: http://www.troublefreepool.com/pool-school/water_balance_saltwater_generator