How did you go about making your water changes and what was your water source?
New water needs to be, at the vary least, the same temp and SG as your tanks water when making smaller changes and when making larger changes PH and Alk should be checked also. What type of water did you use for the changes. If tap, you run the risk of introducing chlorine and a laundry list of other contaminates if not properly treated or run through a RO/DI filter first.
I doubt that moving your rock around was the source of your problems.
Now that you are fish less so to speak. Take it a little slower this time. Make sure the tank is indeed cycled. A cycled tank should show zero for ammonia and nitrites at all times. If tap water is your only option use Aquel+ in slightly higher doses than recommended to treat the water. Invest in a chlorine test kit to make sure you are not introducing chlorines to the tank. Use hydrometer or refractometer to verify SG of any newly introduced water and check PH of tank and new water prior to water changes.
Start with small inexpensive fish and if possible add least aggressive on up to more aggressive specimens. Use google to do a little research on every species you intended to add to the tank and don't let LFS talk you in to anything you are not 100 percent sure of.
The most common phrase heard at the LFS, "sure they should be fine in your tank", this is many times not the case. Remember, these guys are first and foremost, salesmen and often times know less about a particular fish than the customer. The Mandarin for example.
To check the honesty and knowledge of a particular LFS salesmen, ask a few questions that you already know the answer to. If the reply is vague in any way or out right wrong don't believe any thing else he tells you either.
