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?