Can anyone diagnose this problem?

[crossfader]

What's the best way to lower the pH?

Get a bottle of 'pH Down', there's a few brands but all will lower pH.✌

 

[MI420Farmer]

What's the best way to lower the pH?

Purchase a standard bottle of Acid and Aklaline and some testing liquid. Drop a little pH down in and you should be good to go.