The nature of your sourdough starter will determine how much baking soda and salt to use. However, using too much baking soda will give the crumpets a metallic taste, and using too much salt will make them bitter. Only increase the salt to ½ teaspoon if the discard is weak, or increase the baking soda to ½ teaspoon if starter is very sour. If you’re unsure, use the lesser amount.