Dripping Kalk

[bear27]

I just started dripping kalk into my tank and am curious becouse my calcium and alk levels are droping.My ca started at 420ppm and after 2 days its at 380ppm same with my alk it started at 9 dkh and after 2 days its at 6dkh and my ph is moveing between 8.4-8.8

When i was adding these seperatly via seachems reef advantage calcium and reef builder things were always at 420ppm=ca,10dkh=alk

Know im not sure if im just not adding enouf kalk,or if im doing something wrong,and if in fact im not adding enouf how do i counteract the ph flux

pls help