I have a 25gal frag tank and I'm going on a week with my Red Sea Pro Mg test running 1,500-1,600 with no dosing. I've performed 30% and 50% water change. My Alk is moving between 7.8 and then I dose 20-40ml. My Ca is moving between 420-350 with 30ml dose. but no movement in my Mg. SPS sticks are full polyp extension so I'm not overly concerned but I don't want to have some type of crash in parameters. Concerned I have a bad test kit but it was reading changes before a week ago. Any suggestions are welcome.