Hello,
I give my plants some humic acid and that always brings their ph down some. You could try some Fossil Fuel brand humic acid or maybe Liquid Karma with humic and fulvic acids. Just follow the directions on the product for application rates. I think liquid kelp seaweed products like MaxiCrop also mix up low in ph and might help in your situation. All of these things when used as directed are very beneficial for your soil and plant as well.
Good Luck!