I seem to have a problem with my PH. Last week I noticed my PH started going down therefore I added some buffer which kicked it a little bit back up then when I checked again it had gone down some more therefore I added more buffer and a few hours later it was down to 8.0. Scared that it would keep going down I did a 10% water change and the PH slowly came back up to 8.20 but is slowly starting to trickle back down. Do you guys think this is a lack of Magnesium ?

Only thing I dose is Kent Tech A&B for Calcium supplement, Iodine and I buffer the water when needed.

Thanks.