I am by far no expert, and it sounds like your tank is rather new. First, get your livestock out. Second, take a deep breath and relax. As mentioned before, it seems something is wrong with your water chemistry. My tank took almost a year to finally settle, with a lot of losses in that year. I got to a point where I just had to be patient and let the biology do its work for itself. If you start adding things quickly, you will compound the issue, leading to another issue.
Without any livestock, you can dim your lights (if dimmable), take time to adjust your chemistry and get your water tested for silicates or other issues that it could be. There may be the possibility you have a bad batch of salt, so test both your fresh RO/DI water and fresh mixed SW. as you feed the tank, watch the flow patterns in the water, where is everything collecting, are there dead spots? How deep is your sand? Do you vacuum it? At some point the Dino's are going to run out of food and disappear. If your water is clean ( RO/DI and FSW) everything should even out at some point. Then slowly restock your tank with some critters.
The biggest thing I have learned over the last year has been not to rush at all. It cost more money and frustration, which is why I think so many believe this hobby is so expensive. And it is expensive when you rush it. How cool would it be to say "I've had that pair of clowns for 14 years".
Look into a local club, at your LFS, really check out their tanks and ask for advice (if their tanks are struggling find another store) and of course there are so many pros on this sight. Good luck, be patient and don't give up