Its strange that you don't dose any alkalinity and still you read that high in dkh. Your corals should be using and lowering your alkalinity. If you are maintaining your high levels of alk, then it is getting dosed into your tank somehow. Perhaps the Ionic B has a buffer in it? This may account for the alk staying high. I would stop dosing everything, and no water changes. Measure the dkh DAILY and see what your system is consuming over a 72 hour period. Then dose the Ionic B and see if that increases your Alk. If it does, then thats where your getting your high Alk from. Its possible that you are slowly increasing your dkh but at the same time precipitating out your Ca and Mg because your PH is high. This may make you dose Ionic B more and in turn increase your dkh. Keep your PH at around 7.9-8.1 and you will not have to dose Ca as much because you will not precipitate as much. Then, if it was the Ionic B that was slowly bringing up your alk, it should lower. If the Ionic B is the only thing your dosing and its not the culprit thats increasing your dkh, then the answer has to lie within the water changes. Regardless, something is keeping your dkh from naturally decreasing.