Thanks for your reply buddy.
I'm sure you use them with no issues, and I might struggle to fix it retrospectively with organics! I'm going to try to avoid using phosphoric acid as a 'fix' and properly determine the problem then look at the options. I'll try and get a PH testing kit and test the tap water, tap water with nutes and the runoff. Maybe even the soil too. I'd still be reluctant to use PH down just because of the phosphoric acid and it's possible effect on microbes.
The worms sound interesting; are they live?? or worm castings? I'm going to look to amend my next soil with some of these; worm castings, bat guano, perlite, fishbone, blood meal, Epsom salts, sweet lime dolomite.