Thanks for writing in.
The red marks could represent an allergy
or a fungal infection
(This is less likely). You could be allergic to the soap or some thing that you have started using off late like a moisturizer. I dont think this is related to your adrenal fatigue
or leaving diet soda. To relieve the itching, you can take tablet Zyrtec
10 mg once daily for 2-3 days. You can use Tablet Benadryl
1 tablet at night. This will make you sleepy, so dont take it in the day time. I would suggest you see your physician to get this rash examined.