One of the disadvantages of DIY CO2 is the inability to control it fully. The best way to prevent too much CO2 from accumulating at night is to have an air pump come on (i.e. put the air pump on a timer) at night.
It probably will depend on the size of tank you have.
I am currently running a DIY CO2 sugar/yeast mixture on a 6 gallon edge with no air pump running at night.
pH is in the neutral range when I check it.
pH may affect the fishes depending on what type you have in your tank.
Very hard to overdose with a DIY/yeast style CO2 system.
Usually the problem is to get enough CO2 into the water. However, an air pump at night is good insurance. Time it to stop an hour or so before the lights come on. Then the CO2 can build up some so it is there, ready for the plants.