Bath salts are not my area of expertise, but I do make them a few times a year as gifts. I went on a hunt for how to make bath Salts that don't clump or lose scent from baking/being left open, and found a YouTuber with a recipe/suggestion that has worked so far for the non-fizzing salts I've made. She seems fairly knowledgeable from the videos I've seen, but maybe someone with a bit more experience can chime in.
Her suggestion is to add the wet ingredients to the dry powder (baking soda, corn starch, natrasorb, tapioca flour, etc) before mixing in the salt. I haven't tried fizzing bath salts yet with this method, but I plan on doing so in the near future, and will probably add the citric acid at the same time as the salt. Here's a link to her video if anyone wants to check it out, CreativeBathLab
As far as medical issues going undiagnosed or undetected, I feel your pain and am glad you got it figured out. It's honestly a travesty that so many people go undiagnosed for so long, how hard it is to find a great doctor, not to mention health insurance that will actually cover the necessities like testing and medications.