Magnesium has not been mentioned here, and I feel it is important to the chemistry of alk/ ca... I would ensure that if your salt of choice does not achieve at least 1350 tested mag, and you do not dose to meet that standard, then maybe you should pay close attention. Coloration with sps is not quite as easy as most may think... Don't forget temperature and salinity, and strive to ahieve consistentcy with all parameters described. Excess nutrients can brown out your corals, while too low of nutrients can starve/bleach your corals. It is that fickle balance that we all strive to achieve....Good luck....