Many of us don't worry about pH, ever. You can if you'd like, just to see what CO2 does to your pH. But my guess is that with a KH of 17 (really? wow), you won't notice a drop with DIY CO2 at all. But, in any case, a drop in pH as a result of CO2 injection is irrelevant. It won't have an effect on anything. The CO2 that causes that drop, however, will.
If anything, I'd suggest you test your CO2 level instead with a drop checker to get an idea of how much CO2 you're actually injecting into the water column.
You didn't mention how big your tank is, or the size or number of bottles you're using, but generally you're safe with a 2-liter bottle, using a basic sugar/yeast mix and a basic diffuser, per 10 gallons of tank water. There are variables, however, so you may want to start smaller. Good luck!