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.
Causes of Yellowing Leaves. Common causes of yellow leaves on tomatoes include cool soil, age-related death of the lower leaves and a myriad of nutritional deficiencies including nitrogen, boron, potassium, iron and magnesium. Leaves may also yellow when affected by fusarium wilt, bacterial wilt or verticillium wilt.
The most likely culprit, I think, is going to be item (3) above. At least, that is what the problem is in my large tomato garden 95% of the time when leaves begin yellowing and/or curling. If you have bacterical speck, you will notice tiny specks of brown to black to almost purple on the leave surfaces.