Not exactly scientific. But are the plants closest to the worm bin getting a better feed ?

if the bin is bottomless or leaks, quite possibly yes

It appears to me that the plant in the back is getting more nitrogen due to it's height and depth of color. However it could be a different variety than the rest. Hard question to answer without all of the facts.

Yes the bins have holes drilled below the surface line. Tomatoes on left are all either alicante or gardeners delight, indigo rose moving further right.

The alicante is darker