I have to jump in with my 3c of opinion here... I am totally against using baking soda in our gardens. The reason is the chemical composition of baking soda, NaHCO3, meaning it's made of one sodium atom, one hydrogen atom, one carbon atom, and three oxygen atoms. The oxygen and hydrogen atoms are fine, but the carbon atom is added waste and the sodium atom is a problem. Build up too much sodium and the roots will shut down... plants do not like salt. We regularly flush salts out of our soil that are left over after our synthetic nutrients break down, but by all means, do what you can not to add any additional salts to the mix. The problem with baking soda is that it takes so much of it to move the pH back up after adding nutrients, that the added salt does become a problem over time.
A much better kitchen product to use as a pH up is pickling lime, Ca(OH)2 . It is very strong and doesn't take much to raise that pH back up to where it needs to be, and note that not only does it not have salt, but it has calcium, oxygen and hydrogen... all needed by the plants. The only problem is that at room temperature pickling lime is a little hard to get mixed into the solution and you have to be patient with it... a little goes a long ways.
I found toward the end of my synthetic phase of growing that it was easier to use lye as my pH up, which you can get behind the counter at any hardware store. Again, a little goes a long way, but it is also a salt... it is just doesn't have the extra carbon atom to add extra waste to the soil and you use so little of it that the salt isn't much of a problem.
As far as pH down, lemon juice works, but it takes a lot of it to get good pH movement, and as it breaks down it attracts bugs to your soil. I needed a clean and cheap pH down, and I found it with battery acid, H2SO4. I would have preferred to use phosphoric acid, but it is a little exciting doing that chemical reaction at home and it is a bit expensive to buy.... but look at the chemicals in sulphuric acid... 2xHydrogen, 1xSuphur and 4xOxygen. This is all useful to the plant, with no waste! To safely use battery acid, just buy a $6 box at your local auto parts store, and a gallon of distilled water. Take out one cup of the distilled water and replace it slowly with one cup of battery acid. You now have a 15:1 water/acid mix that closely approximates the acid content of the popular pH down product at the hydro stores.... and you just made enough to last for a year, for pennies.