With it only being cycled about a month, the cycle may not be complete. You need to check for ammonia. At the minimum you added too many fish too fast. With a newly cycled (if it was) tank and adding 4 fish at once, that probably started another mini-cycle. The fish were stressed enough but being subject to ammonia will definately kill them. 25 pounds of live rock is no where near enough for that size tank either. 1-2 pounds per gallon.
What is your salinity levels? Many aquairium stores keep a low salinity level like 1.021 since it is cheaper. Most home aquariusts keep a higher level of around 1.025. If you just got them home, floated the bag for 10 minutes and let them out with that big a salinity swing that alone could kill them. Going lower to higher is very dangerous to the fish as it causes organ damage/failure. I always bring a refractometer to the store to check their levels. NEVER rely on what a salesperson tells you. When salinity levels are different you should drip acclimate your new fish before adding to the tank over about a 30-45 minute period.
You need to test for Ammonia and Nitrites. Nitrates are really not that important for a FOWLR tank.
