Rcs Massacre

I have 6 rcs in a 4 gallon with full Monte Carlo carpet. I have had them for 2 months. I do weekly 30% water changes. I do co2, but I skipped it today. When I came home, my regulator had malfunctioned and done 3x as much for a normal day of co2 for roughly an hour. All my shrimp died. It might be the co2, but does anybody have any ideas?

 

co2 is toxic to them, that is surely the cause of death, as is for humans and most animals
sorry for your loss, I just use liquid co2

 

I'm getting ready to get my first rcs. Sorry to read about yours.

Will you try again with new ones - or go with something else?

 

I'm getting rcs again. I usually have One bubble every other second, but for some reason, my CO2 went up to about 2 to 3 bubbles a second. I did a large water change, so my tank should be good to go, right?