Ammonia / Nitrate spike

Good morning,



Looking for some help.



I have a 55 gallon tank. It took 3 weeks to fully cycle before all levels reached 0 and things were perfect. I have 50lbs of live rock and live sand.



I added in 2 clown fish and a clean up crew and for the last week - 2 weeks everything has been going great. So I added a Goby also.



Yesterday, my ammonia jumped up to 0.25ppm and PH to 8.4. So I did a water change taking out 10% of the water and also cleaning all equipment.



Today I have a shrimp and 2 snails dead and Ammonia of 1.0ppm with Nitrate of 10ppm. My Nitrite is steady at 0.



One other thing I did after the water change was reposition 2 live rocks which I have now read can cause spikes.



Any ideas if this could be the reason? Or dead shrimp? It was removed as soon as I found it in the morning.



I have added some EasyStart Bacteria Booster to try to help out...



Any advice? What should I be doing to help reduce my levels again?



Thank you so much for any advice!!