Tomato question

Tomato question

Hey everyone, I've been watching this community for a while, though this is my first post. I hope to make friends with other plant loving folk :) I am growing some tomatoes, and a few of my plants have been flowering but then shriveling and dying, without setting fruit. The problem seems to start a bit father back on the stem, not just the flower going, but a portion of stem as well. Anyone have any idea what has caused this? I'd appreciate any insights :)
Our light set up seed thingy

Our light set up seed thingy

The Hoya saga

The Hoya saga

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My New Apartment!

Canopy

Canopy

Happy Beltane!

Happy Beltane!

Todays Pix

Todays Pix