You need to get those dead fish out as they are just decaying and probably are causing a huge ammonia spike. What you need to do is pull apart that rock and get them out. Don't buy any of those "miracle cycle" chemicals, as most are pretty much a waste of money because you need to cycle the tank on its own without the help of something. Here is what I would do if I was in your position.
- get all fish out of the tank, if this means removing the rock for a little bit then do that as well.
- put rock back in so there is no die-off.
- let the tank sit for a while and make sure you test your parameters every day. Do the tests yourself, do not bring them to a LFS to test, and do not let someone else tell you what they are. You need to test pH, Ammonia, Nitrite, Nitrate, and Salinity every day so you can get used to testing them and get into the habit.
- when your ammonia, nitrite and nitrate hit 0 (nitrate as close as you can get it) then add a cleanup crew. I would only use snails, no hermits if you can help it. I would get different types as well as each are very good at getting rid of certain algaes.
- after a week or so with the clean up crew I would buy a fish, preferably something hardy like a clown and continue testing every day, or at a minimum of every other day. Make sure that your system is stable enough to handle this fish while your fish sits in QT. After a minimum of 2 weeks in QT you could add him to the tank and continue testing.
- Keep testing and make sure that your system has balanced out again after the new addition, and I would wait about 2 weeks before you purchase another fish for your QT (which would be 2 weeks). This would keep you at a pace of one fish per month.
Good luck and remember, adding things quickly always takes longer!