First post, so no doubt I'll get something wrong
I have grown tomatoes from seeds this year, and have 18 plants. A mix of:
Tomato 'Mountain Magic' F1, Tomato 'Shirley' F1, Tomato 'Sweet Million' F1
They were super healthy (and still are), have just started flowering and the first green tomatoes are appearing and I've noticed nearly all of them are starting to get a dark stem, starting at the bottom, but also in some cases where any branches spread out. The colour is between a soot colour,grey/black and purple. The leaves are all healthy,no spots, no fungus, and all plants are flowering and are otherwise very healthy.
I'm not sure if its a sign of lack of nutrition(I feed tomorite at alternate feedings), too much water (I water every 3 days) or a blight. A blight would be strange as its all fresh soil, from seed, and grown in 4 different locations around the garden (albeit they all started by seed in the greenhouse).Or because I went on holiday and came back and they had massive suckers on, so I removed probably a third of each plant that wasn't needed.
I'm from North England so it's only about 10 degrees at night lately, too cold?
Really at a loss, is it benign or the death of all tomatoes?
This is a vid of 1 plant, as you can see I only learned to focus half way through:
If anyone can advise would be really appreciated