Your cya reading is higher than I like and like the pool lady said, the only way to lower it is to do a partial drain. I like my cya reading to be between 30-40. If you decide not to do a partial drain, you can live with cya of 90, but you'll just have to run higher than normal chlorine levels as a result to avoid an algae bloom. See the chart at the following link. Ph and alk look good.

http://www.poolforum.com/pf2/showthread.php?t=365

Watermom