ALk at 14.4, Please Help!!

[LeanneP]

Tank is 90 gallons. I am doing a 15 gallon change to begin with. I checked and the alk is 13.7 down from 14.4 so it is coming down. Ca is about 420. I just cleaned a power head that was really plugged up so things seem happier with more flow. It amazes me how fast algae can grow in 6 days. Hoping the sps will be happier after a water change and some more cleaning.