Hey Herb potman, I am a noob too. I have experience keeping saltwater reef tanks, so I can help explain things a bit. As it happens, I was searching for the same answer as you, importance of PH for organic/slow release fertilizers grow methods.
PH Down is going to be an acid, and PH Up is going to be a base. The warning label is there to alert you to the possibility of chemical burns due to them being low and high PH solutions. They should be fine to use with Fox Farm Organic Soil if used in the proper amounts.
I am planning to use a Blumat system and will be using water from my Reverse Osmosis De-Ionization system. Specifically after the RO stage and before the DI stages. I did not want to have to PH my water so that I can take advantage of a pressurized storage tank solution to push water directly to my Blumat valves. My RO water at that point is about 6.8 - 6.9, so I figured I was good, but wanted to check.
As someone suggested, getting a water filtration system to filter your city water through would help to correct the PH as well as giving your grow nice clean low contaminant water. I would suggest using an RO filter, with sediment, carbon and finally a Reverse Osmosis stage. If you have chloramines in your city water, you are going to need a big honking carbon block after the sediment and before the RO membrane to protect the membrane from chlorine as chlorine will destroy the membrane.
The microbial life in your soil will help to bring the PH down, but providing the proper range of water will be better for all parties, your plants, the microbial life in your soil and you in the form of a better chance of success.
I hope that helps.
