No not a good idea.

Playing the Ph up and down game is not good for the plants. The liquid drops have a large error factor. They have a plus or minus of 1 full point and that is to big of a swing for most of us. If you want your Ph at 5.5 and with the error factor if 1 point plus or minus you can have a Ph of 6.5 or 4.5 and guess what you missed the number.

You should try to get a real Ph pen....they only cost about 40 bucks these day's on eBay.