water change and usage is the only way to lower ALK.
if your ALK gets too high, its major problems. if it gets too low, things look poor and then receed, but recover easier.
to raise your ALK, you can dose, and raise instantly (backing soda, or alk powder)
check your water change water, because most "REEF" salts have high ALK and CAL so thats also why it takes soo much water change to lower such a small amount.
i keep mine 8-9 because corals will tell you when its too low and a easy dose is all you need.
while too much becomes a major problem......