Browning stems but green inside?
I'mm not sure what is going on with my plants, there seems to be ten thousand explanations online and none of them seem to fit perfectly. I live in Los Angeles in an apartment so I grow my organic brandywine tomatoes in a "spa" pot that you water from the bottom. They were doing great until they started to flower, when the bottom leaves began to yellow. I cut off all yellowing and this continues for some weeks but now there just seems to be an overall wilt with dark blue/black spots on the leaves. The stems are turning brown in the middle of the plant--they are green at the stem and green at the very top but the middle is brown. I cut some stems and the inside was perfectly green. I found brown dust on my hands from handling affected stems but was not able to "rub off" the brown color, so it wasn't just the dust. I grew this plant from a seed and feel sorry to see it doing so bad. Should I start all over or is this plant salvageable? Here's photos: