I have had a single tomato plant growing in a raised bed for months.
It had achieved a spread of about six feet and a height of three feet
with lots of blossoms but no fruit set. I tried root pruning to no
avail.

Four days ago, in desperation, I dumped a gallon of 0-10-10 solution
on it. Now there are a lot of little green marbles that (I hope) will
become luscious, juicy, sweet, tangy tomatoes soon.

Just passing along a tip.