Adjusting pH is tricky.
Test your soil a few times and a few different depths (1 inch, 4 inches, and close to bottom of bucket). If the worms and your compost isn't bring the pH into the range for your plants, then slowly and carefully add you adjusting powder.
If your soil is too acidic (below 6)– add a base. The most common base is lime. There are four types of lime for gardens, but my favorite is pulverized. Add a small amount around the top of your soil (or mulch) and water. Test again in a week.
If your soil is too alkaline (above 8) – add an acid. I am an organic gardener, so I use leaves, vegetable scrapes, and grass clippings. All of these will help to lower the pH in your bucket garden’s soil. The worm droppings also helps in lowering the pH in the soil. Add a VERY SMALL amount of sulfur, water, them test in a week.