My red sea max tank has been going great for the past few months. It is 75 gallons and I do a weekly 20 gallon water change with clear sea salt and ro water. I check the main parameters and so far so good. I also dose Bionic at 1 once a day with both parts. Last week i did a water change with Ro water I made a week and half ago. My green hammer, kenya tree, frogspawn all look really bad. My cnadrian coral died in 5 days. I checked my water parameters, no amonia, nitrates, nitrites,Phosphates were in line, Ph 8.4 alk a little high but not off the chart, Calcium was 400 ppm, the magnesium is a little low and my salnity is a little suspect, it tested 1.019 but my tester read 1.023. I did another 25 gallon change today and raised the salinity to 1.022, what could be killing my corals, they were doing great a week ago, fish are fine but i did lose a cleaner shrimp, i suspected to a bad molt. any suggestions?? thanks