Tomato Disease?

[genericname]

I just started my hydro tomatoes in early November. A month after seed germination they are quite tall and very full. I have noticed some discoloration on them. There is also curling of the leaves but that is probably an over-watering issue.

The discoloration is yellow and is spotty at times. There are also portions of the leaves dying, turning brown but not falling off. I am picking them off with my fingers. I have cut entire branches off the lower portions because the entire branch of leaves is brown (note, the actual branch appears healthy - only the leaves die). I'd rather not destroy a month and a half of work due to a disease, especially if I can fix it. Any help is greatly appreciated!