Add some dolomite or hydrated lime to your flush water and flush until the pH is ~6. Because this will likely wash out most of your soluble nutes, you should use your brita filtered water and make your normal feeding solution at pH 6.5 and afterwards pour through until some comes out of the bottom. Don't water again until the soil is good and dry, because your'e really going to make things soggy with this.
Don't use baking soda,.. it has a lot of sodium and it's better to use lime to minimize the salt,.. lime is calcium hydroxide/oxide and dolomite also has some magnesium hydroxide/oxides. Your plant needs those more than sodium.
