Timmer

I bought a new Caldera Geneva about a month ago and am suddenly having problems maintaining consistent chemical levels. It has the inline cartridge system that holds a bromine & mineral cartridge. My alkalinity & PH levels starting dropping and I can't get them to back to normal. I've tried shocking & several tablespoons of spa-up and haven't noticed much of a difference. I also replaced both the bromine and the mineral cartridge and it didn't help. Also, the bromine level is running a little high - I assume I can just lower the number setting on the bromine cartridge? Any advice appreciated! Thanks