It’s so frustrating to have obvious problems and get no answers! I would certainly pursue the possibility of autoimmune disease with a rheumatologist. These symptoms could all be related and sometimes symptoms precede lab evidence by months or years. I had symptoms of lupus for 10 years before my lab work showed a positive ANA. Lupus can certainly cause tachycardia and rashes. There’s autoimmune based hearing loss. If afib was documented on your ECG you should be on a blood thinner to prevent clots and stroke. If you get a rash again it should be biopsied with immunoflourescent studies. Sometimes lupus is diagnosed based on a skin biopsy of a rash. I would also want full thyroid studies done including anti thyroid antibodies as Hashimotos, an AI thyroid disease common in women can cause both tachycardia and afib and is treatable. In addition, you might review signs and symptoms of lupus, the quintessential AI disease , to see if you have any other symptoms, like sun sensitivity, joint pain, hair loss, etc. I know that sounds like a lot but unfortunately the burden to get diagnosed seems to fall on the patient these days, especially when multiple specialists are involved and symptoms seem unrelated. I hope you get answers soon!