Just throwing this out there, but maybe there is not enough nutrition in your tank. It takes more than light and good stable parameters to grow coral. You may have a biological deficiency. As someone has said before carbon dosing may help. Macrobacter7 helps some people. Did you start with Ocean rock or dry rock. I am sure over the two years you have had this tank you have brought in different types of bacteria but there may be something that is killing it. If you are doing regular water changes etc., a ICP test is really not going to help you. It will only tell you what you are deficient (or in excess) in. if you’re doing regular water changes and you are not having corals using up your elements. A better test may be a Aquabiome test. That would at least let you know if you have any pathogens or if your bacterium is out of balance.
aquabiomics.com