Worm castings are not usually that high in Nitrogen. What are you feeding your worms and what is the bedding?

Have you fertilized or mulched with anything else other than castings?
How is the weather?

What were your methods last season?

Perhaps your soil had lots of locked up nutrients but limited soil microbes to make them available to your plants. Now that you have been adding castings you have increased your microbe population and unlocked all that high nutrition?

A soil test might be in order to figure out what happened this season and what you should do for next.

What types of plants in particular are not setting fruit? Perhaps some tomato bloom spray would help? It is supposed to work on other plants in addition to tomato.

" ... the only difference this season ... "
the weather is different every season, as is soil composition, and the uptake of various nutrients is affected by soil moisture level and temperature .... if you have less bloom and set, try adding some higher P fert to help bloom, higher K to promote fruit growth .... have you limed the area? excess calcium can affect the uptake of potassium, an imbalance of calcium and boron can cause less bloom and no set ... the problem isn't that you have an excess of anything, you have a lack of something, or an imbalance .... in short, it's unlikely nitrogen in the vermicompost has anything at all to do with it

Bill