Bree,
If corals are suffering, you need to find out what your alkalinity, calcium, magnesium and pH levels are. Don't know why these chemistry components are important? Here's a link from Christy's great Reference Library to help you understand testing and adjusting the chemistry in your reef .....
http://www.reefkeeping.com/issues/2006-06/rhf/index.php
HTH
And happy reading