Do you know your taps Ph by chance? If not you should put some tap water in a cup/dish and aerate it (or stir it off and on) for 24 hours to gas it off and test to see what the actual ph is. Reason I'm asking is I'm curious as to what Ph your water is starting out as.
Also in an established tank you don't need to use the Stability. Your BB is mostly in your bio-media in your filter. Plus with a Ph as low as yours it's not working anyway. So all that being said, test your tab ph as described above, stop using the stability, get the crushed coral in your filter, but right now add 1/4 teaspoon of baking soda to get some buffers in the water and test to see what your ph is tomorrow. If your DW is truely dropping your ph that low you might actually have to use both crushed coral and baking soda. You'll have to see how well the crushed coral works and if it needs help you might have to dose baking soda after WC's even with the crushed coral. Right now it's hard to say until you see how well the crushed coral is going to work in your tank.
Also in an established tank you don't need to use the Stability. Your BB is mostly in your bio-media in your filter. Plus with a Ph as low as yours it's not working anyway. So all that being said, test your tab ph as described above, stop using the stability, get the crushed coral in your filter, but right now add 1/4 teaspoon of baking soda to get some buffers in the water and test to see what your ph is tomorrow. If your DW is truely dropping your ph that low you might actually have to use both crushed coral and baking soda. You'll have to see how well the crushed coral works and if it needs help you might have to dose baking soda after WC's even with the crushed coral. Right now it's hard to say until you see how well the crushed coral is going to work in your tank.