how to change PH?

I have PH up and PH down that is used for my spa. Can I use this to balance my plant water PH or will it kill them.

I dont have a spa so I dont know what chemicals you use on them, I would assume that since its for such a large amount of water it would be stronger than the PH down/up they sale at hydro stores which is usually phosphoric acid for down calcium carbonate for up. What are the chemicals, it should say on the bottle, that would be a little more informative.

i wouldnt use spa PH up and down. go to HOME DEPOT and you can find some cheap $5 small bottles of PH up and PH down.