i recharged my 1 liter co2 bottle last night around 8pm. i used 1 cup sugar and 1/2 teaspoon yeast. i just bought some really good wine yeast so i was interested in trying. the little reactor was going crazy last night discharging bubbles very frequently. i woke up around 7am and checked ph and it had dropped to 7.0 over night. i think i overdid it with the yeast. is that kind of ph change so rapidly ok? i'm not sure what tolerable change limits are regarding ph. all my fish seemed normal. its a 42 gallon tank and i didn't expect such a rapid change. it put my co2 from 7ppm to 19ppm overnight.
You're fine. If you're really worried, watch the fish closely, and run an airstone if they display O2 problems. Fish react differently, in my experience, from pH changes due to [CO2] rather than changing Kh drastically or TDS.
19ppm isn't that much CO2.