PH HELP. ph up not working!!

Hello, having a problem with my water. I'm using foxfarm liquid nutes and once I add the nutes to the water my ph goes way down 5.0 ph. I got to add some ph up usually to get it back to around 6.5ph. Now here is where my problem is. It seems like I'm using alot more ph up then I use to. I have to add alot of ph up and at times seems to be doing nothing to raise the ph. What's going on here? Should I maybe ph first before adding the nutes or is my RO filter be going bad? Or does ph up go bad?

Maybe check the calibration of your meter?

What is the make of your pen, do you have any other means to test pH besides that pen?

You always pH when after you put the nutes in not before.

insomnia65 said:

What is the make of your pen, do you have any other means to test pH besides that pen?

Click to expand...

I have a Apera pen. ph 20 model I believe. I did test with 7.0 solution that came with kit. It was at 7.2

How much up you been adding to what amount, what is the water, well, rain, RO, tap, distilled?