Help! I am unable to lower my alkalinity

[Keramio]

Hello,
I've been struggling with my alkalinity lately. First it was about 12 dKh but lately it is creeping towards 15 dKh. The corals are starting to look a bit off wit their color. I tried doing a lot of water changes lately. But with little to no succes. I used Red Sea coral Pro salt. But I switched to a new one with 8dKh on the box. All other parameters seem fine and stable. Can it be caused by too much carbon dioxide in the room? Or any suggestion on how to solve this.
PS: I haven't dosed Kalkwasser for half a year now. Yet the alkalinity keeps growing.
Thank you for any advice.

 

[SPR1968]

If you do a series of 10% water changes with the new salt mix the alkalinity will lower

Coral Pro mixes to around 11-12 as standard and so it always will be on the high side

 

[KStatefan]

Is your salinity also moving up?

 

[Keramio]

Is your salinity also moving up?

No my salinity is also stable.