Ph up drops are very dangerous as they change the PH way to fast and you can kill you fish and it is unstable so the PH will go down again in a few days. It should be brought up over time with minerals like calcium for fresh water and salt water. Coral calcium has no actual sea salt in it so it can be used for fresh water tanks. It is great to add a bag of for planted tanks to just to stabilize the ph. I do not know what type of tank/ situation you have so I can't be specific.
I never mess with the PH purposely on my tanks using chemicals... too much can happen, and yes, sometimes bad PH swings can cause fish problems due to stress etc...
As Vanman said, if you really need to alter your tanks PH, it maybe best to choose a more natural method such as crushed coral pieces etc...
^ it isn't a very bright idea. PH changes by drops are so sudden it stress the fish out, it's like when you are used to be warm then suddenly a cold chill comes by and gives you cold or so. But for the fish's status, the effects will be bad and not beneficial, well you don't want those unwanted things to happen..