My newer tomato shoots are turning black and I'm urgently trying to figure out why. All the plant sites are unanimously convinced that it's late blight, stem canker or a related fungal issue, but the plant simply doesn't display symptoms for these diseases- there are no lesions or sores, only a gradual darkening on shoots that is mostly uniform. If I look very closely, I can see many individual (very small) black dots. Any ideas? Thanks in advance!!