Hi! I'm growing three different varieties of heirloom cherry tomatoes in a big pot on my patio. They have grown very big (with pot, nearly 5 feet)...but a while ago they started developing brown circles on the lower leaves...and then yellowing. I researched diseases, and it looked like it might be early blight. I cut off the diseased leaves and mulched...and then later, when more were affected, I cut and sprayed with baking soda solution. It is still spreading. Now it`s doing all sorts of things...curling and browning on the edges, yellowing first. Is there any hope for the plants? The upper branches have tomatoes growing. Will they be able to finish growing? Should I do anything else? I think I should have tried a hardier cultivar for my early growing efforts...but I was dazzled by the heirloom varieties.
lower leaves on tomatoes will yellow and wilt when plant diverts the nutrition to creating fruit. I am almost certain that the yellowing is from that, however I have never seen the blackening on the edge of the leaf like you have posted in the middle picture. I could only venture a guess about this, but since you are growing them in a small container, it is possible that the roots are getting too hot, or may lack water. I don't believe it is bacterial since there is no yellow edge between the dead and live tissue.
The darkened areas on the leaves look more like late blight, although it is pretty early for that disease here. Usually it doesn't appear until the Fall rains arrive, unless there is substantial rainfall during the Summer. If you've been using overhead watering frequently, that might trigger the disease. If it is late blight, fixed copper spray controls it pretty well, if you spray before the main stem gets infected.
