You can have up to 6 additional email accounts in Comcast besides your primary account. Sign on to your primary account and click on the Users & Settings tab at the top of the page. You should see a link in blue underneath your user name that says Create Secondary User.
Some tomato plant leaves yellow due to a lack of sunlight on mature plants. When the plants become large, bushy, and heavy with fruit, the top portions of the plant can block the lower portions from getting sunlight. This can cause the leaves to yellow, and is really nothing to worry about.
Purple under leaves of tomatoes is a trait of phosphorus deficiency. This is the most telling trait of that deficiency. The yellowing of seedling leaves (lower part) is the deficiency of a mobile nutrient. The plant takes the nutrient from the lower leaves and moves it up to the growing portion at the meristem. Phosphorus is a mobile element.