Hearing your daughter started having the same rapid heart beat too makes it seem obvious that in your case it's not caused by taking too much baking soda.
I don't know if it could be candida. I tend to think too many people blame the wrong symptoms on candida. To know if it's mold exposure, simplest thing to do is for you and your daughter to stay in another residence for a couple of days and see if both your heart rates improve.
Let's go back a tad, is both your increased heart rates constant, or is it like a roller coaster throughout the month, or even day?