Help With KH

[Madreefer]

I'm using a Salifert test kit and my KH is at 15. It came with a 7.5 check test and it tests at 8.0. I assumed that the kit was crap but after doing the test on the check bottle that came with it now I'm a little concerned. My KH has always been at this level. Everything else that I have tested for is good. Cal 420/MG1440/PH8.3/ sal 1.025 My parameters have been like this for 2 years. How is this possible without a meltdown? I'm running a calcium reactor with a bubble every 2 seconds and the effluent is a steady drip at 6.51. But according to the test kit it is at 7.3 Also a Kalk reactor that runs with my ATO. What do I do to bring it down? I also think my colors should be alot brighter, I think they are a little on the brownish side.