o.k., pool gurus...my ph is in the 7.5 to 7.8 range, cya is in the 40-50 range but i can't seem to keep the clorine level up. it's testing 0 - .5 ish. i keep dumping bleach in and it'll come up a bit, but i'll check it later in the day and it's back down to near nothing. i got it to shock levels last week. do i need to shock again? why can't i get it to stay up? thanx for the help.