Sounds like you have some die off, which is quite natural for uncured and for most 'cured' LR
. Unless you cured the rock yourself or know exactly where it came from, how it was cured, and transported, you should expect some die off. This will start the nitrogen cycle in your tank and is therefore a good thing.
You should be checking your water parameters for Ammonia, Nitrites and Nitrates.
When Ammonia and Nitrites readings are zero and Nitrates are down (under 20?) you can start adding livestock.
I suggest reading the articles on this site as a good start.