no problem. you may want to just use a regular powder buffer to raise your KH to an acceptable level and then use the two part additive to maintain it. you will need to monitor KH daily untill you can find the right portions of the 2 parter to maintain your current levels. be sure to add the two part buffer in the morning. the KH portion has an extremely high PH. you don't want to overshoot your ideal PH range -7.8-8.5. KH will be consumed at a much faster rate than calcium, so you won't need to test for CA as much. Another thing to keep in mind, is that unless your using a PH probe, it is hard to get accurate results from a colormetric test kit. 7.4 sounds really low. I have a feeling its not as bad as you think. Live rock can start to disolve and a PH that low.