Just read the last couple pages and have seen that you have been losing coral. I am not sure what you have looked into but one thing to look into might be exposure to copper. The things you describe sound very similar to people who have some small source of copper in their tank and don't know it. Just throwing that out there. I have been on the end of a tank on the downhill so I know how frustrating it can be... however mine was due to lack of time therefore I can only imagine how frustrating it can be when you have no clue what is going on. Good luck revamping your system and hang in there!